Well, I just got a Magnaflow cat and XL 3 chamber muffler on 2.25" pipe.
Other than the added decibels, I'm not feeling any difference in my ride.
The tech told me any bigger than 2.25" (which he wasn't exactly confortable with in the first place) and I would start losing enough back-pressure to lose torque for high-end horsepower.
I didn't want to lose torque so I agreed to the 2.25" pipe.
I drove it around for about 20 mins and decided that the noise level was far too annoying to keep. I went back and had them install a baffle in front of the muffler to quiet it down. It's still loud but more of a contained annoyence.
I haven't reset the ECU yet, so I'm not sure if I will see any performance gains out of this setup.
Maybe it's there, but I'm sure the gain is small if any.
Any suggestions? The engine still seems to choke at high revs. For example, if I punch the gas at 65mph, the revs float around 6 grand with little increase in forward momentum.