The bosal shorty is a catless pipe that replaces downpipe (1st cat after turbo). You still retain your stock 3rd cat as that pipe is known as the catpipe. A full length downpipe replaces the downpipe as well as the catpipe. I went with the shorty option as it was only $110 shipped and safe to run stage 2 with. I was looking at getting a full length catted downpipe to retain a cat but the shorty just seemed like a better deal since i am only running the stock turbo. If a decided to upgrade i will go with a full length DP. If you tune with an AP then you won't throw the P0420 code for cat insufficiency as that code is deleted by the reflash so you can go catless if you want. If you can find a decent ful llength catted DP for the right price i would go that route.