fitted the xforce 3" highflow cat the other day (onto full 3" exhaust). very happy with it.
seems to have gained ~1psi extra boost, so i have to figure it has improved flow somewhat. the exhaust note got a bit deeper, but not really louder, although slightly droney now at certain rpms.
i'm considering a resonator somewhere after the cat, to quieten it down a bit, get rid of the drone. this wouldnt affect flow, would it?