BMW Exhausts is a site featuring the BMW exhausts that are made by BTB Exhausts. Whether you run an E30 325 track car and need a 6 branch manifold or want a full race system for your E46 M3 - these guys should be able to help. They used to supply Prodrive with the E30 M3 systems when this model was racing - so they know their stuff.
Site for BMW exhausts
