I had (its sitting in the garage right now) a modified X-50 exhaust, where the internal baffles were removed. I ran this for 9 months. Much better sound than stock, and you could really feel the faster spoolup and I gained 0.1 bar boost.

Great low-cost solution for a first exhaust, rather than switching out these $3-5k exhausts that these guys with big $$ like doing.