If you get a MPS then a 3.6 shouldnt be an issue IMO...I do know that I had a 3.5" with a T-Stat, plugs, 3" exhaust (no cat, res. or u-bend, stock DP), CAI, and PCM and I still had KR. Dropped to a 3.4, got PEM's and a DP and 1.84's and a new tune. No KRSo it all depends. I would still get a 180*, DP, and AT LEAST a PEM (front).
Then I'd say scan, scan, scan, and drop to a 3.5 or 3.4...
IMO = in my opinion
PEM = ported exhaust manifold
just get a set of headers, they are getting retarded cheap now.