problem...

my 95 camaro 5.7l lt1 has now a 96 impala lt1, hooked up to a 95 wiring harness and runs ok but has a low vacuum and service engine soon light on, and ABS inop light, stuck hardcode "ecm circuit problem" rich exhaust smell, the guy who replaced the engine said i have a plug in my exhaust had inline cat tested was fine, and the canister when reved deep growl/pop noise coming from that side. i want to know why i have low vacuum, could it be the cat or do i have another problem, and could a clogged cat cause all those problems, and if not how could i start to get rid of some of the problems. thank you and i want to hear anything anyone can help me with.

sounds like you have a bad vacuum leak somewhere....and it has nothing to do with your cats.... check all of your vacuum lines.... example.. egr maf map..etc....or your computer is shot... lol

I don't understand why you are using a 95 wiring harness. Why didn't you use all the wiring from the Impala? Chances are they are different. Did you check that? Are you still using the computer from the Camaro? Sounds like it. Why didn't you change the computer? The engines and computers go hand-in-hand. That could explain all those computer related problems. Sure it will run with the wrong computer but will it run right is the question. You may have looked at this stuff already but you don't specify, so this is what I suggest.

i agree...