If I were to put longtubes, dual cat y-pipe and still retain the rear O2's on my 96 SS, would the rear O2's be too far away to read the exhaust properly? I know they need to be heated up enough to function right and I'm under the impression that the rear O2's are not used for emissions purposes but to help the computer determine if the cats aren't functioning correctly. I assume most guys just put in O2 sims for the rear O2's or disable them. But I would prefer to keep the computer happy and reading everything. Any thoughts?

 

By installing the 02 sims., it is cheap insurance to eliminate the "what ifs?" You could go through the effort of modifying your y-pipe with rear 02 bungs and runnings some new post-cat 02 sensors, and you may still get a check engine light. It might be cheaper/easier in the long run just to run the sims. and call it a day. Even though I am running dual cats., I still have sims. and it passed emissions with them.