you sure the timing is right? backfiring generally indicates timing is off or something with ignition.

http://shbox.com/1/cam_timing_ani.gif

 

timing good, put a new harness from nookandtranny.com, plugs are new ac delcos, new plug wires, and it still starts to backfire after a few minutes from the exhaust.

With process of elimination only other thing it could be is the opti right?

 

guys never come back and tell how the issue was fixed, so here we go.
95 camraro z28 lt1 with a 92 vette lt1
I used the harness(93-94 camaro) from nookandtranny.com that connects the opti to the engine harness.
used oem opti for 92-94 corvettes/93-94 camaro
ecm was 95 camaro z28
I was down for 5 weeks because the dumb original shop didnt wire everything back correctly so I had the car towed to a race shop (white racing in warren,mi) that specializes in building any and every thing. They taxed me 525 to diagnose and rewire my harness because wires were cut and a whole bunch of ****. They told me this should have been a simple drop in drop out swap. Long story short you get what you pay for.

There was never any thing wrong except that things weren't wired correctly. I contacted visa and I will be getting my money back as soon as I fax and send them info that the race shop gave me on my invoice. For those that dont know always pay with a cc so you have protection and recourse when things like this happen