Originally Posted by doz
The o2 sensor for the cats has NOTHING to do with the air/fuel ratio. There are o2s before the cats that do this.
Exactly so what you should do is buy an off-road (no cats) h-pipe/x-pipe or y-pipe if you are going to a single mufler because it will come with bungs prewelded for the rear O2s. Then take your truck to a tuner and get him to turn off the rear sensors so your truck runs in a "closed loop". No check engines lights then.
All the good longtube kits (Kooks, ARH, Dynatech) will come with O2 bungs welded in.