Rage91GT

Hey all just a quick simple question I'm sure. I am removing the pre cats and cats off of my 91 Gt I am planing on going from manifolds right to an H pipe. My question is what do I do with the wire that is plugged in near the cats? Also what is the proposed horse power gains.. Thanks.

mustangGT86_05

That wire is your o2 sensor, you need it. Just be glad it isn't in the cats or you'd have to fabricate a bung hole into the pipes. Also, most likely will see a loss in hp, as NA cars require backpressure to run right. Factory may include a bit much of it, but you don't want to take out too much. Keep in mind removing cats is not legal.

cookcobra

You should have 2 O2 Sensors, by the way. They must be plugged in to the x or h-pipe because the air sampling that they perform is reported to the computer, which then calculates things like fuel mixture, etc. Best to just keep all the smog stuff in place and modify around it.

AdderMk2

Get an off-road mid pipe
swap your O2 sensors into it
don't hack up your stock mid pipe, the tubes are only 2.25" where a new midpipe will be 2.5"