The exhaust won't do much by itself. I think 5 HP and a couple lbs of torque is probably a good guess. The sound is nice though. smile

Thing really liven up when you add a good intake like the SLR or K&N AirCharger to the exhaust. Just based on my experience and that of others in PNWX I would say the following is true (these are guesses):

Gibson Exhaust alone = 5 HP
K&N AirCharger alone = 8-10 HP

K&N + Gibson = 20+ HP

Seriously; the difference was huge when I got both systems into play. Now for the cams, throttle body and some headers! laugh
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ChuckH
"Every morning when I wake up I know it's not going to get any better 'til I go back to sleep again!" Al Bundy