I tried a different intake plenum and I went with a 2.5" catback exhaust and while it does seem a bit spunkier, it's not a huge difference, and it's all pretty much above 3,000rpm that I notice. Being our 3.0's are more rev happy than some motors (peak HP is around 4750rpm) it does seem to have more high end for passing and stuff, but I don't notice a huge difference otherwise. Going too large with exhaust will hurt backpressure, but betwene the 4.10's and the slushbox, I don't notice anyways. The intake was a waste of time over factory, but I do feel I got my money's worth for the exhaust. As far as "mapping", my shop claims my higher flowing exhaust was causing a "lean condition" and was tripping my CEL and they had it for 4 days trying to solve the issue before drawing that conclusion. I'm more apt to believe it was bad fuel because after switching from E85 (which I ran at the time) to gas for two tanks, and now back to E85, the CEL has never returned since I ran gas. Unless you're cracking the motor open and REALLY modifying the hell out of internals, I don't see the sensors failing to adjust for any (slight) difference from intake and exhaust.