Normally trawl the A4-B6 forums but I have been asked by a mate to investigate if possible to replace his 180bhp TT-8N single pipe exhaust with a twin pipe version? Is it a simple case of changing the backbox - and of course the bumper lower spoiler, etc. or does it require a full exhaust replacement perhaps back from the CAT? Would it be cheaper to go for a perfoemance exhaust - say Miltek?? Can anybody advise or could point us in the right direction if already covered on previous threads. Thanks.