Catback/Downpipe on K03

[kpowell911]

Hi guys, starting to quite enjoy my Mk5 now, even though its stock with just a Ram Air. I have the K03 model so I know its never going to set the world on fire performance wise, but I think If I can add a little more power and more importantly, noise Ill enjoy it even more.

Ideally, Id like to keep the stock cat, I cant be arsed with the MOT hassle.... I also want some nice looking Tail Pipes for when I fit my ED 30 Rear Valance..... So Im pretty much decided on the Miltek 2.75" Resonated CatBack.

https://www.awesomegti.com/shop-by-car/volkswagen/golf-mk5/milltek-2-75-cat-back-exhaust-vw-golf-mk5-gti-and-edition-30/

However, I've read ideally the gains/improvement come from the downpipe. Guessing I need to buy/find an aftermarket downpipe that works with the stock cat so my system will go:

Stock Turbo --> Aftermarket Downpipe --> Stock Cat --> Miltek Cat Back

IF thats the case, what down pipe do I need?

Second of all, what is the 'PreCat Removal'? I've heard this is a good option for the K03 cars, but would the after market downpipe erase this too or is it completely separate?

Thanks

[colesey]

The stock downpipe has two cats, of which the precat is the one closest to the engine and is there for the German MOT which tests cold start emissions. It is irrelevant to UK testing and creates a huge flow bottleneck. Knocking it out is a free mod which lowers the exhaust gas temperature and gives earlier spool up. Zero impact on emissions for MOT testing and a slightly deeper exhaust tone. Better mpg too.

[pudding]

Bashing out the precat helps above, but the main restriction is where VW crimped the pipe after the cat to clear the gear cables, which then exits into a rather wimpy 2.5" pipe.  The best flowing and best value DP is the track slag one.  Be aware a DP of that size increases exhaust noise quite considerably, even with the factory cat back.

[Octoparrot]

The stock cat is part of the standard downpipe so I don't know how you're going to keep the standard cat with an aftermarket down pipe.