Here is the story... Me and my father built a custom 383 out of a GM crate motor. We wanted to retain the stock TPI setup(88 Iroc 5.7L 350 with 700R4 [ABYA prom]) and of course burn a new prom. We had a few bumps along the way but got where we are and that is lost. This car is not getting proper injector pulses. I burnt chip after chip, played with the timing and finally took it to a shop who told be the problem i knew from the beginning. They are telling me i must run a carburetor or aftermarket EFI system if i want it to run properly. I was having the same issues with the stock motor which makes me think it was a sensor of computer issue, But the shop hooked up a new ecm and prom and still had the same issue. PLEASE HELP!!!! I have alot of money invested trying to do this right and want to stay with the TPI if possible. The heads are off the late 70's, The heads are 1.94/1.6 valve size,The specs on the cam are 290/300 adv duration, 222/230 @.050, .468/.480 with 1.5 rockers, 110lsa..... It has 1.6 rockers so the lift is actually .499/.512 at the valve. --34lb. injectors/New water pump/New starter/New underdrive pulleys/new distributor/new plugs & wires/Griffin radiator/New heated 02 sensor/New Headers/Everything has been replaced except the intake setup and ECM. Firing order hasn't been changed and electrical/vacuum lines all seem to be fine. Thank you guys for all of your help with my project.

System1

That is the problem you need to find out, if it was having the problems before the swap then u gotta resolve what that was.

An aftermarket fuel system is NOT needed to run a 383, but tuning can be a pain if your new to it.

By a pain what kind of problems would you say may be going on? thank you for your response.

System1

I'm not sure what you mean by injector pulse, still learning this junk myself. Still though from what I've read once you get into higher performance you may need an adjustable fuel regulator or better than stock fuel pump? And I hate to ask, but sometimes it's the small things like a new fuel filter.