I recently had the TurboXS Catless Stealthback Exhaust with the 4 inch downpipe exhaust installed on my 2004 WRX. Over all I would say that it is a well crafted, quality product. Good welds, nice finish, and fitment was seemingly perfect. Other than the turbo to downpipe gasket all the necessary hardware was included. Along with the exhaust I had a Grimmspeed Up Pipe installed as well, and finished off with a Cobb Accessport to handle the tuning aspect. Performance wise, there is a major difference, the car has been woken up substantially. Turbo spools much faster and pulls alot harder, although top end power nearing redline still leaves something to be desired, mid-range power has increased ridiculously. There is also a substantial audible difference when it comes to the turbo, unlike the exhaust note and noise level itself from inside the cabin (this is a "stealthback" exhaust afterall..).. However, from an outsiders perspective, that gorgeous low growl of a Boxer rumble we all desire to unleash has clearly been let out of the box (no pun intended??). With the stock axle back, it is a bit raspy at certain RPM's/loads, but nothing too harsh. In my opinion, the turbo whistle more than makes up for it. I would definatly reccomend this exhaust to anyone that is looking to unleash some power with out attracting any unwanted attention with an obnoxiously loud fart can of an exhaust.

I hope that my review has helped, here is a demonstrational video to further my explination.