I had my gutted cats replaced with straight pipe... and the sound is night and day. SOOO much more aggressive with little to zero droning (a little bit around 2k rpm) compared to my gutted cats. Got rid of all the noise coming from the engine/cats. 2.25'' pipe used manifold back, into a 2.5'' Magnaflow DI/DO w/ built in x-pipe, into 3" chrome tips. Amazing! Recommend this setup for any 4.6 bird/cougar who wants a clean aggressive sound!