> I have a 5000Turbo test pipe for a cat, and it's exactly 2.5 inches. I would guess that most of the rest of the exhaust was smaller, but that gives you an idea at what it starts... try 55 mm, seems typical. that's approx 2 1/4" -- Huw Powell http://www.humanspeakers.com/audi/ http://www.humanthoughts.org/