The SLP's come with the downpipe. Then you have to use the SLP cat with the rear O2 sim. I don't know if there is another alternative. The downpipe's flex part makes an unreasonable amount of ticking noise. You have to wrap it well with thick header tape.
Jack
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JackO
2004 GTP CompG. WS6, 3.29 axle, HUD, tapshift, Premium sound, XM radio, leather, sunroof, 17inch 5 star chromies, BFG Comp T/A. Wizaired CAI.
Traded in. 2003 GTP. Every option but HUD. New Mods: Wizaired CAI, SLP Headers, Cat, U-bend and Downpipe, 3.2 Modular Pulley, Phase 3 rollers w/OR Pushrods, Larger Belt Tensioner Pulley, Gatorback, AL103's, 180 Degree Stat, DHP