Hello,
It seems I've seen posts on here before about people removing their AIV system and it doesn't hurt the performance of the truck, but I cannot seem to find anything at the moment. I'm replacing the downpipe that connects to the exhaust manifold, and I would like to remove the AIV system (that connects to that downpipe) if at all possible. Could somebody chime in with their experience on doing so? I hate to weld up that hole in my pipe, only to have to hook the system back up if it doesn't work out. Thanks in advance!!

AIV system? don't know what that is. The holes in the exhaust is for the o-2 sensor. You plug those up your engine will run like crap.

Suprised somebody with a 4cyl hasn't responded yet. On my 91' V6, the tube running from the exhaust is part of the EGR system. It does work to lower CO emissions and my truck won't pass SMOG without a working system. The truck will run fine without it as I found out when my EGR valve failed and I didn't know until I failed SMOG.