I am getting a custom turbo done this summer to my GTS, gonna cost 10K, rebuilding most of my engine and changing pistons, rods, etc. Lengthy process, around 3 weeks for this application on mine to be complete, but in the end...300hp to the wheels, that's what I am aiming for, the guy that is gonna do it said 10k to hit those numbers. So if you want numbers in the upper 200's or even 300 like I'm going, going custom is your safest bet. If you want to go with the XS kit, make sure you replace your pistons and rods. Our high compression pistons currently on are not good to turbo to. Maybe a small boost would be ok to the stock pistons, but anything over 5psi, without new pistons you're asking for trouble. Good luck man.