Heres one for you. 87 GTA pulled the motor and dropped in a 383 recently. No VATS. Pulls up no trouble codes. Been through 3 custom chips 2 computers. All voltages check out at the ecm pin-outs with the ignition on but not running. I know for sure the fuel pump primes the system. I can keep the motor running by pedaling it, but it eventually wants to die. By holding the pedal at approx. 33% throttle, the RPMs will rise to 3K and drop to 1K at a frequency of 1.5 seconds and will cycle this way before eventually dying. I tried unhooking the crane fireball ignition box and using the stock set up and no change. I did get it to idle for 2 minutes one time.? Any suggestions are welcome.