Swapped MPFI motor runs lousy

[AlsTVR]

I've got a camaro 3.1 motor and 5-spd, using a Fiero MPFI system (heck, I just liked the looks of it) installed in an old british car (TVR... its a tube-frame, fiberglass body 2 seat sports coupe). I got rid of the carbon canister, the EGR and the vacuum valve that controls them. I'm using a complete Fiero computer system except I retained the 3.1 camaro injectors.

It's run to limp around the block, but never runs right. Cold starts OK to a smooth idle at 1400 RPM for a few seconds then RPM slowly drops to stall. It may do this dozens of times. If I can get it a bit warm, idle smooths but engine pops and sputters on throttle opening. Fuel pressure is OK and vacuum seems good til RPMs drop toward stall. Timing light says I'm close on that so I guess I screwed up on the hoockup of the computer or something.

If you've got a suggestion, I need help! If no solution, I'll be forced to get rid of that pretty MPFI and stick in a grungy old carb.

[evilmiata]

Is your fuel pressure staying up when you open the throttle? Did you solder the harness? Are you sure that the fuel injectors and spark plugs are on the correct cylinders?
Use the timing light to check each cylinder and see if any are mis-firing.

[AlsTVR]

Thanks. Fuel pressure tracks up and down with vacuum just as it should (drops by 5-10psi to about 35 at hi vacuum and rises to max of about 45 when vacuum drops at throttle opening). Checked all plug wires but haven't had an easy way to check injectors. Unlikely tho since it runs smoothly when it decides conditions are right to run, and the Fiero wiring harness is so tight that I can't have hooked them up wrong.