I have to pump the gas about fifty to sixty times to get it to start after it has sat for a while. After it starts it runs rough then smooths out.

Good question. All you can do is hook a line up to the fuel rail to get some gas so you can inspect it. If the gas looks ok they you probably have either a fuel pump problem or ignition problem.

You have to find the reason the check engine light is on. This will aid in diagnostics. Also, are you buying fuel at the same place both times?

check cylinder compresions,sounds like there low(worn rings)by the way the 5.7iroc is one of the worlds best engines.....

no its lossing its prime after its first prime the diagham is bad in the check value.

I just recently have been fighting the same problem with the same make/model/year vehicle. For myself, I would drive off and on through the day and it would run fine. Then suddenly after a start it would run rough and die. I would have to wait 20 to 60 mins before it would start again. I had it checked and fuel pump was only putting out around 19 psi. It should be around 41 psi. Had fuel pump replaced and no more problems. Furthermore, now it runs so much better. It's funny how over time I didn't notice how the performance was slowly degrading. Unfortunaley fuel pumps for this car run around $300.

if it's carburated, make sure your butterflies are opening.

Could be anything. Can you tell me what you've checked? the more info the better.

you need a new fuel pump

i would say that you have a bad fuel pump or if you have a carb on it the float inside the carb is stuck check these and i'm sure you will find it's one of these.

since the car sat for 6 months it could be a vaccuum line the lines are rubber or hard plastic the tend 2 dry rot or chewed by small rodents, while the car is running listen 4 whistle or check for cracks or lines off completely