i'm using a otto racing muffler, i bought it from http://www.procarparts.com (very cheap and sounds lovely)
http://www.procarparts.com/store-detail.asp?sku=UNFB03%2D5614MFX
last spring/summer i build a new exhaustsystem for the car, 2,5" from after the intake (?, not quite shore what it's called) one smaller muffer under the car and the otto muffler at the end... sound very nice, sounds even better now that i have changed my airfilter into a "racing one"