I have a stainless steel decat pipe for a VW T4. Mines a caravelle, but fits transporters.
The pipe replaces the section with the cat - improving performance and fuel economy. Being stainless steel its set to last a while. The cat isnt required on diesles in the Uk, so this is a legal upgrade.
Ive replaced the entire exhaust recently for a custom stainless steel on my 2001 T4 - hence this is for sale.
(I do have the original cat aswell, which is for sale separately at £30).