ok so my set up is a 1990 formula was originally 305 tpi 700r4 speed density.I swap in a lt1 with a 700r4 I converted the intake for a distrubtor and it's running the stock tpi Ecu and wiring harness.the motor is stock except long tube headers the problem I am haveing it's it idles fine driveing it easy it does ok feels like it's lacking power but when I accelerate it doesn't miss but feel like it's hitting a rev limiter and falls apart before the shift and once it gets to maybe 4th gear around 3500-4k rpms it's got nothing just falls apart.my fuel psi is 38psi and 43 with the reg UN hooked.I have a new fuel filter,plugs,cap rotor wires,coil,and o2. the Ecu was a mail order with the knock disabled do I need a retune or do I have another problem? thanks

 

You're going to need a tune to compensate for the short runner length, added cubes, and exhaust.

Could be either your pickup coil or ignition control module. Both of those can cause rev limiting symptoms.

 

it has the the Ecu tuned thru a mail order so I don't know how on point it is I forgot about a bad pick up thanks