After I installed my pacesetter lt, and offroad y now the car starts a little hard, idles rough and when I put it into gear it starts backfiring at a steady pace what the hell?

 

I don't know if these things could cause your problem but it should be easy to check these, make sure your plug boots are on and on all the way, and make sure you plugged your o2's back up ohh and you could have two of the wires mixed up (ie number #2 wire on like #4 or whatever else is on the side with the #2 plug)