My 95 z is giving me trouble. My ses light is on and at wot the timing is back alot!!! this doesnt always happen though , car runs strong has no backfire. i have no cat on the car and it has open race readies so it is LOAD. maybe knock module? maybe opti? maybe 02? i had codes ran a while back and i think it was a fuel trim code rich or lean i dont remember? what is the box that is on the front of the d.s. valve cover,(silver box with heat sink fins on it?) car has mild mod. tb bypass, ported maf, k&n, . any idea guys? whare should i start. car has 62k miles thanks jeff

 

The noise from the exaust might be causing the knock module to retard your timing. Usually headers set it off but your exaust might do it too. I'd say get an LT4 knock module. It is not as sensetive as a stock LT1 knock module.

 

find out what the code was and start there. thats what diagnostic trouble codes are for. to let you kjnow that there is a problem.