Check the condition of the exhaust. The bend under the drivers seat seems to rust first due to the rainwater being thrown up by the front tyre and the mid section halfway down the van is also prone to rust. Exhausts can be expensive for some engines....
ETKA - Audi B5 A4 2001-2003 Exhaust System Part Numbers (pdf) Mapco.de Cross Reference Brake (pdf) Mapco.de Cross Reference Part Numbers (pdf) Mapco.de Part Numbers Application By Manufacturer (pdf) Mapco.de Part Numbers Application List (pdf) MBT VW & Audi Catalogue Rev2 (pdf) Pagid ...