I just got done putting the L98 in my car. It's a 90 T/A with a ZZ4 cam and headers. The ECM and wiring harness are from an '86 along with the TPI setup. The problem is that it will start for a second, then just die. It stalls. I have spark, the timing is dead on, and I have 45lbs. of fuel pressure at the rails. VATS is operational so I can rule that out of the equation. Anyone got any ideas? I hope so . This thing's been pissing me off for a month now

vacuum leak - severe

Fuel pressure in the rail when it dies?

You may not like my idea but get a laptop and a data cable and hook it up. Its costly but it'll tell you more than you know now.

I don't have a wiring schematic to look at but if you're using a 86 harness and you have a Vat's system running thru the ignition I would guess something in the ignition circuit is cancelling the spark delivery after it momentarily starts. You can try to shoot some ether or spray some gas mist thru the throttle body once it starts and see if it will continue to run while you're spraying fuel into the T/B. If you can keep it running for abourt 5 seconds then fuel will be the problem. Do you have a fuel gauge you can leave hooked up on the fuel rail to monitor it once it starts? Is your MAF sensor plugged in? I think the '90 T/A already went to a MAP system also, if that's true, I don't know if the distributor would be compatable with the '86 ECM. These are just a couple of wild guesses right now but it's a start. You do have gas in the tank???

Do you have power to the injectors? Do you also have the ground pulse from the ECM?