A9P computer

I got my first fox last weekend, a 91 GT with goodies. I am new to fuel injection as was my only car was a carb. So can anybody school me on computers for these cars and how you can tune them? I have 19lb injectors with heads/cam/intake, and I feel this isn't enough fuel even though this car hauls. I'm wanting to do a 100shot and get bigger injectors, so my question is will the A9P computer work or should I go with the A9L? I ran into a guy that had 13 foxs' and he said he ran the L on the majority of them. whats the significance of the L? Thanks

Ryan