hard to start

I have a 92 ford ranger 4cyl/ 5spd that i use for my daily driver and for about the past 3 months it has been hard to start and when it does start it idles rough. It is especially hard to start in the mornings, but not always,after the first 2 days i figured out the ritual to start it is to hop in crank it for about 10 seconds then stop and crank it again and it will usually start after about 10-12 seconds of turning over. oh yeah as soon as i stop cranking it, the first time, it makes a poping sound that comes out of the exhaust it knda sounds like backpressure just poping out. i have done a comlete tuneup such as changing all 8 spark plugs, and wires, air filter, fuel filter, oil. I figured the tuneup would at least restore the little power it used to have but it didnt. Any help you can give me would be great. Thank you