I've had my intake and magnaflow catback for over a year, someone posted dyno results on youtube showing a 10-15 hp increase, I can say that after installing the test pipes a couple weeks ago, I do notice even more improvement in midrange torque and a definite better throttle response and my mpg is even better with the less restriction.
Do you have any other mods?I wouldn't recommend 'gutting' the 2ndary cats. It's a PIA & that sh*t inside is lethal. You have to make sure every bit of it is removed. I replaced my 2ndary cats w/test pipes... and WOW, what a difference!! Better throttle response, better mid-range torque. Best $140 I've sent so far.