The original Audi 'long-life' exhaust on my 3.0 litre A4 B6 Avant Quattro was starting to rust through on the rear pipes and boxes, so I started looking to replace the whole exhaust. For interest this is what I found.

The system is substantial with a a twin centre box back from the cats, and two large rear boxes. Neither Euro Car Parts or GSF offered an exhaust for this model. Kwik Fit didn't seem to have the car in their system, but anyway a new Golf exhaust I saw being fitted there looked lightweight. The Audi OEM price was a staggering £1385 (inc VAT) for three boxes and the new clamps and hangers needed. Ringing round, I couldn't get the Audi price discounted anywhere.
Eventually I saw a complete new exhaust system with all mounting parts, made by IMSAF, an Italian company advertised on eBay from Germany (Blackert and Schacht) for £460 with a £60 delivery charge. I checked with Alfa friends who said that IMSAF had a good reputation. So I ordered, and just three days later DPD delivered it to west London, struggling with a very heavy package in thick cardboard. The exhaust quality is very good, correct shape deep drawn boxes, heavy construction with good welding and finishing. Now I just have to fit it when it gets a bit warmer.
After failing to find a good exhaust (regular, not noisy) from UK sources I recommend this German /Italian alternative.

dick101