I have a 475hp 383 Stroker I just dropped into my '91 Camaro over the weekend. We ended up using a FAST EZ-EFI system in place of the old TBI. The FAST system had a kit that came with a 255 lph inline fuel pump. I installed it leaving the factory pump in the tank per advice of some other people. I however seem to be having several problems related to fuel delivery. Under fuel or heavy throttle the car goes/stops like crazy as if there isn't enough fuel being supplied to the engine. The car will also just die while driving down the road, After doing this is almost impossible to start. The car is VERY difficult to start after it's been sitting and is at air temp. Plus, my fuel economy with this new engine is about 8 mpg, Which from all i've read and heard is obsurd. From the engine build to the guy who did my transmission said with this cars setup and rear end I should expect around 15-16 mpg, maybe better if I'm light on throttle. I'd expect better from a 4bbl carb. Anyways, I believe I read somewhere that the GM pumps in the '91 Camaros only flow at a rate of 133 lph. Could this be my problem?

 

Given that it was an RS, and thus a TBI car - could possibly be an issue with the intank stock pump not feeding enough fuel out of the tank.

Is the factory in-tank pump running still?

If it's not running, then that is your problem - can't suck fuel through a non-working pump.

If it is running, then might just be not enough fuel - the TBI pump only had to feed 170hp.

 

Yes, it is running. I was going to rip the cars computer out so I didn't have to look at the check engine light until I noticed the pump needed the factory computer to operate or do a hot wire to the battery. I just decided to leave the factory computer in for the pump and will pull the engine light bulb out of the dash when I get sometime. As far as the flow goes, I also thought I read somewhere that the factory pump was also setup for lower pressure since TBI really only needs like 16 psi or operate. That might be a part of the issue also since I have my reg. set to 50 psi. The thing bounces all over the place half the time, from 20's upto my 50 preset. Anways, guess I'll be dropping a tank this weekend I was hoping that was it was and not a engine or FAST problem.