You're not going to blow you're engine @ 4PSI. It is a lot more in depth than you think you can really budget a kit together I've even seen those Ebay kits succeed for years of driving at a solid 7 psi the whole time but I don't suggest it, the turbo and manifold are definately the last 2 places you wanna cheap out on. Also it's got to be intercooled, you don't HAVE to but it's retarded if you don't and bad on the turbo. It's really in depth but good luck to you and keep posted up along the way and pictures.