You can either get a catback already made from:
pfyc.com
3800performance.com
wbodystore.com
and a few other vendors.
OR you can buy the mufflers, DP, cat and resonator (if you want) separately then go to an exhaust shop and have it installed. BTW, you can upgrade the pipe size from stock. Get quotes from a few shops.
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DHP V1.0, Slotted rotors, S/S Brake Lines, Custom CAI, GMPP Handling Kit, KYB's, Jimmy C DP (U-Bend delete w/ Hi-flow cat), Flowmaster Super 40's, drilled 180° T-Stat, Alt. Rewire & Alt. Voltage Booster Combo, 605's, ZZP Motor Mounts
"The only difference between me and a madman is that I am NOT mad!" - Dali