I can't figure out whats wrong with my Lt1. Today i replaced the fuel filter hoping that it would help, but anything past 5000 rpm, and my car will not run right. The motor fades in and out and runs choppy, somtimes as low as 4500rpm. Its not the plugs/wires, replaced them 10k miles ago, and they are properly guaged etc. Car is running mostly stock with only a cold air intake. Ive heard there could be a couple things contributing to this. A mass airflow sensor? Opti? Any ideas or ways i could diagnose the problem?

My car: 96 z28 74k miles 6 speed.

 

with 74K miles you could be running into Opti issues, that'd be my first guess if all the plugs/wires are ok, but it sounds like an ignition problem if it only occurs at high rpm.

 

it also could b ur knock modual, im not stock but mine does that same thing at high rpms, it retards timming and it sucks... just my thoughts....

 

Could it be the cars cats clogging up?

 

if its the cats, i'm seriously considering taking them off and sticking a piece of pipe where they were. They don't check emissions where i live.

 

thats fine if u kill the cats but where is ur o2 sensors, u may have to kill the o2 sensor in the comp as well or it will runs orse then it does now....