BMWs have dual exhaust, or "twin" I should say. Pipes are only 1.5"-2" on most of them, but the newest 7 series (2003 or so) has a decent sized exhaust, as well as vacuum actuated.
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ASE: Brakes
Yea..that very well could have been the most retarded idea I've ever heard, but .. do it anyway. -TheShow50h