I have a 2000 S4 and if you want to plan to put the K04's on be prepared to spend over 10,000. Just a chip from MTM or APR then see if you want more Hp. Because with a bigger turbo it is bolt on but you need to drop the engine and do some slight cutting of the engine bay to have them fit, you'd also need a complete almost straight exhaust system to let those turbos breath, you'll need new intercoolers, a new clutch, a new fuel system, new air intake and MAF, new DV's and a few more things. believe me if you don't have a big bank account to do this right now, wait...it'll be worth it. But with all this You can expect to see upwards of 450hp and 490lbs/ft on 100octane higher gains are very possible.