I just recently got my car back from the engine shop with a fresh 306. Everything I have is new except for the igniton and an aftermarket chip...I havn't installed them yet. Here's the problem. I can get to about 3500 rpm before it starts to break up and even backfire horribly. Is this because I havn't changed the stock ignition, or is a new chip really that important on a modified engine? I'm running roughly 50 lbs of fuel pressure on 24lb injectors. Please help...i'm frustrated.
