Best performing systems are the rather pricey tuned pipe units from Mac's Mufflers and Toni Clarke that can turn an 18x6 in the 10,000 rpm region. For the majority of us sometimes financially challenged folks, side dump or pitts style mufflers from Abell, B&B Specialities, Bisson or JTec work quite well giving an increase of approx. 800 rpm, with the pitts style Bisson and Jtec mufflers being the quietest.

Karol