I run a round ss Magnaflow w/2.5" pipe, same as this:

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It's surprisingly quiet for the size but has a deeper tone. for a little while I removed the airbox and had a cone filter on the maf, it got louder when stomped on but not raspy. before it heats up it sometimes pops and snaps between shifts.

2.6 Trooper
2.0 Impulse Turbo