I just purchased a pacesetter header for my 2.2 ecotec sunfire and i was wondering what will all have to be done to get it up and going. what i am doing is getting it installed at a shop and upgrading the pipe to 2.25" and getting a highflow cat from magnaflow (http://www.car-sound.com/catalog/universal/530.aspx) P.N. 53035. wil my o2 sensor plug into the sensor boss the 53035 cat comes with? also would anyone recommend taking off the resonator? is there anything else i should know such as what has to be welded, does any of the downpipe have to be cut off(i heard the pacesetter goes from a 2.25 to a 1.75 which i found odd) thanks for the help!

I'm not so sure about the O2 Sensor but I can kinda help on the other things.

Yes the Pacesetter header shrinks to 1.75" at the end of the downpipe so you'll want to get that piece cut off, especially if you want to have a full 2.25" exhaust system.

I would have the catalyitc converter welded into place instead of clamped into place.

As far as taking the resonator off, it depends on whether or not you want a raspy exhaust?

For example, I have the Pacesetter header for my Ecotec, Magnaflow Cat and Magnaflow Single Exit Cat-Back system, all 2.25". I don't have a resonator what so ever and it is raspy but I dont care how it sounds, as long as the system expells the unwanted gases then i'm happy.