I'm having problems with my 94 z28. It only has no cat, cold air intake, and throttle body bypass. For 2 weeks my car has been slowly dying and I just can't figure it out. I've replaced all wires and plugs twice since. I have a miss that I can't diagnose. at low speeds and rps it misses and hesitates also some sparck knock heard also when I ride my bike behind my wife driving it when she gets on it it blows black smoke so it must be burning fuel. When you get on it it runs better but you can still tell a miss in it. Also just started a popping heard in the engine like up through the intake. I've logged and logged still no ses light and no codes. it's a 94 so no misfire code, every now and then it'll throw a low map and egr code but they'll clear and not come back for a while. I've sprayed all over looking for vacuum leaks but nothing. I just want to know what it is not knowing is killing me and I need to fix it please help

 

I've also replaced the fuel filter since....

 

Triple check those plug wires

 

It sounds as though your optispark ignition is failing. They will typically exibit some symptoms n the way to failing, begining with an uneven idle, then random missing. Finally missing and cross-firing will result in non drivablity. The cross firing will often cause a "backfire" into the intake manifold, as the plug may fire in a cylinder while the intake valve is still open.
Takes 4 to 6 hours to wrench it yourself, as water pump removal is required.

Hope this helps

 

Yea I'll take my manual out there and verify the firing order on the wires and make sure they are right.. On the optispark should I replace the whole thing or can I just replace the cap and button?

 

Replace the entire unit with a GM opti.