VW 1.8T Downpipe (8-10HP gain) - $250-350

Downpipes are a direct replacement of the stock VW 1.8T downpipe to the catalytic converter.  The theory behind a larger downpipe is much like that of a performance exhaust system, better flow.  The factory downpipe is quite restrictive, therefore the addition of a larger downpipe will add approximately 8-10HP.  Not only will a downpipe increase power output but it will also help the turbo spool up faster. There are two sizes of downpipes available 2.5" and 3".  There is much debate over which is better, but it can be assumed that when used with the stock ko3 turbo the 2.5" is great, but for any larger turbos you should use the 3" system for peak performance.  Note however that many people have used a 3" downpipe and cat mated to a 2.5" cat-back with excellent gains. It all depends on what your plans are and how deep your wallet is!