Every car enthusiast knows the drill — you add more power, and your engine gets thirstier for fuel. Eventually, that means upgrading your fuel system to keep up with the demands. For my 1993 Mustang, this upgrade had been on my to-do list for a while, and when I saw Holley’s Sniper EFI 340-liter-per-hour fuel system (PN 526-25; $899.95) upgrade designed specifically for fuel-injected Fox Mustangs, I knew it was time to make it happen.

Holley offers this kit in two variations: one with -8AN lines and a 525-liter-per-hour pump or with -6AN lines and a 340-liter-per-hour pump. Since my build isn’t pushing past 500 horsepower, I opted for the -6AN kit, which will perfectly match my combo. Plus, I added a set of ACCEL 48 lb/hr injectors (PN 150848; $527.95) to ensure the right amount of fuel delivery without overcomplicating things. (Editor’s Note: Adam is a Holley employee, but he is a true Mustang enthusiast that wanted to share his build with us and we thought the value of this content outweighed any inherent bias. We hope you agree!)

So when the UPS driver finally knocked on my door, I was like a kid on Christmas morning. Opening the box, I was immediately impressed by the sheer number of fittings and accessories, including Mr. Gasket clamps, extra mounting brackets, bolts, AN fittings — you name it, it was in there. Holley did not skimp on making this a complete kit adaptable to just about any installation scenario.

But let’s be real: the highlight of this kit is the drop-in, OEM-style Sniper EFI 340-liters-per-hour fuel pump, which can be used in a stock fuel tank and supports as much as 700 fuel-injected horsepower at 60 PSI of fuel pressure. Alongside this pump, the braided fuel lines, sleek black anodized AN fittings, and the adjustable fuel pressure regulator with gauge had me itching to get started.

Part 1: Tank Removal

Before getting started, we lifted the car in the air. With the Fox up on jack stands, I relieved the fuel pressure and then disconnected the battery. A quick tip to relieve the pressure: simply unplug the fuel pump relay, crank the engine a few times, and boom—pressure relieved. Trust me, you don’t want to skip this step unless you enjoy a face full of gasoline.

Next, I crawled underneath to disconnect the fuel lines at the tank — the high-pressure line, low-pressure return, and the vapor line. The high-pressure line requires removing snap clips with a flathead screwdriver, while the low-pressure return line needs a quick-disconnect tool. The vapor line? Just give it a few solid tugs with pliers and pull it off.

With the lines disconnected, I removed the filler neck bolts and electrical connections. Removing and lowering the tank is straightforward, as only two straps are holding it in. However, if there’s a lot of fuel left in the tank, do yourself a favor and pump it out into a gas can. This will save a lot of unnecessary struggle. So using my two-jack setup (since I was working solo), I carefully dropped the tank and prepped it for the new pump install.

Part 2: Fuel Pump Install

With the tank out, it was time to get the new Sniper EFI 340-liters-per-hour pump in. Removing the stock fuel pump was as simple as using a screwdriver and hammer to knock the retainer ring counterclockwise until it popped free. After pulling the old pump, I installed the new Sniper EFI unit with the included fuel filter screen, then tapped the lock ring back into place using a brass drift so as not to create sparks while securing it firmly. Before reinstalling the tank, I assembled and attached the -6AN pressure and return lines to the fuel pump.

If you’ve never built AN lines before, it’s a pretty straightforward process. But you’ll need a few tools: vice jaws to hold the fittings and a specialized AN wrench (I recommend getting two) with protective inserts to avoid scratching up those beautiful anodized fittings.

Here’s the quick breakdown: Cut the braided hose cleanly with a hacksaw or cutoff wheel, push the female AN bell fitting onto the hose while twisting, and then thread in the male fitting until snug. Once you get the hang of it, it’s only a few-minute job per line and can even be performed on the vehicle once you have the process down pat.

With the AN fittings attached to the hoses, I bolted both to the fuel pump. Then I installed the new vapor valve and hose, then connected the wiring — black to negative, red to striped positive, to the OEM wiring harness plug that I cut off from the original pump assembly. Finally, I was ready to reinstall the tank — but this time with the help of my neighbor, making the process much easier.

With the tank and filler neck bolted back up, the last thing was to attach the Holley Fuel Filter and AN junction to the two fuel lines I built. After thread-tapping and attaching both, we mounted them with the Mr. Gasket Clamps to the original fuel bracket bolt locations. This couldn’t get any easier; it was time to move along!

Part 3: Fuel Line Installation

Now that the tank was back in, I plumbed the new fuel lines along the body. Removing the stock fuel lines was relatively easy being that most are bolted in, except for one bracket that required drilling out a rivet. Once out, I figured out the new line routing. For guidance, Holley provided a route with bracket mount locations along the transmission tunnel in the directions, but I opted to run the lines along the return fuel line path instead of the transmission tunnel, which felt like a better setup for my build.

After routing, measuring, and marking the correct lengths, I ended up with the feedline length at 13.5 feet and the return line length at 12 feet. Once cut, I marked each line with colored tape: green for feed and white for return (to know which one I was working with) and attached the AN fittings to connect the fuel filter and junction. I then began routing and securing the lines along the body using a mix of brackets provided in the kit, along with drilling some locations for sheet metal screws to hang them along the way. For several of the brackets, I reformed the shape and customized them with a fresh coat of black paint to keep things subtle. A little personal touch never hurts.

Part 4: Fuel Pressure Regulator and Final Lines

Things were moving along nicely! It was time to mount the fuel-pressure regulator for the return inlet and outlet and then attach both the feed and final return lines to the OEM fuel rails. For the regulator, Holley suggests mounting it to the top of the strut tower bolt using their included bracket, but I wanted a cleaner, more discreet look. Instead, I installed it inside the fender on the backside of the strut tower using an additional bracket supplied in the kit (and painted it black, of course).

I then test-fitted the return inlet and outlet AN fittings on the regulator to make sure it had plenty of space. Once I was good there, I mounted the regulator, attached the fittings to both return hoses (inlet and return), and bolted it all together — thus completing the regulator setup. Lastly, I attached the pressure gauge and then both the feed and return lines to the OEM fuel rails using two AN fitting adaptors (feed and return) purchased from Jegs. Finally, I stepped back to view the final setup, and it looked clean. I was ready to fire this car up! But there were still a couple of tasks left to complete.

Part 5: Fuel Pump Relay

The next task on the list was to address the fuel pump relay. The Holley kit I purchased includes a 30-amp relay and wiring, but my ‘93 Mustang GT already has a 30-amp relay with 10-gauge wiring to the relay and 12-gauge to the pump. Since that was more than sufficient, I opted to keep my factory relay setup for now, though I advise that you check your factory relay and wiring to make sure it is nothing less than this – or if you are installing the 525-liters-per-hour pump kit, you need to upgrade the relay. So for this story, I’ve provided a simple diagram in case your car needs the upgrade.

If installing the relay kit, here is a simple diagram. Plus, the Holley kit includes everything needed to perform the tasking including wiring, fuses, and wiring loom.

Part 6: Fuel Injectors

Now I was down to the final piece of the puzzle — installing my new 48-lb/hr ACCEL fuel injectors. To do this, I needed to remove the upper plenum of my Trick Flow R intake. This meant unbolting the throttle cable bracket, disconnecting vacuum hoses, and removing the six 10mm bolts holding the intake in place.

Once the upper plenum was lifted off, I removed the four bolts on the fuel rails, lifted them, and swapped out each injector. I had to be extremely mindful when disconnecting the plastic injector wiring connectors, the retaining tabs are very delicate and brittle. With the new ACCEL injectors installed, I reassembled everything, torqued it down, and double-checked all my connections.

The First Startup

With everything installed, plumbed, and tightened, it was time for the moment of truth. I turned the key, let the fuel pump prime, and with fingers crossed, fired it up.

Success! The engine roared to life, fuel pressure was steady, and not a single leak in sight. I dialed in the fuel pressure regulator to 50 psi, and the idle set in. What a great feeling! This was one of those projects that, while time-consuming, was 100 percent worth it. Now, with a fully upgraded fuel system, my Mustang is ready to take on whatever power upgrades I throw at it next!

With Holley’s Sniper EFI fuel system and ACCEL injectors installed, our Fox Mustang is ready to deliver optimal performance.

Overall, this upgrade wasn’t just about better fuel delivery—it was about peace of mind knowing my Fox Mustang’s fuel system is as solid as the rest of the build. So if you’re considering a fuel system upgrade, the Holley Sniper EFI fuel kit is an excellent choice, whether you’re chasing big horsepower or just ensuring your car reliably gets the fuel it needs.