Originally Posted by euro_2nr

How the hell do you figure that the K04 is an upgrade for a B5 and not a K03s?? My B5 came with a K03s and doesnt mean theres a power difference between mine and a ATW or AEB engines. Once tuning is calibrated to the stock turbo the difference is ~5chp, which is hardly noticible on a butt-dyno. And it is a an upgrade even on a AMB engine. HP is up to ~250 and torque at ~280 with supporting mods. What Kwik_shift is talking about is that there have been cases where the K04, being such a small turbo spools very fast thus creating an insane torque spike which have been known to snap connecting rods which result in a open head surgery. For the $$$ and time spent on a K04 i'd rather get the APR 1+ and have little less power but more reliability for less $ and headaches. The only reason I would get a K04 is if my K03 sh*t the can and I needed a cheap replacement (not upgrade). The K04 can be ran w/o software but you won't see any gains since the mapping is still being sourced for a K03. BTW, what brand is that K04??? If you would STFA a little more, you would find out that the K04 sucks if you're looking for more power and the best thing for the $ and practicability for a new enthusiast is the GTRS. Great quick spooling turbo with mediocre high end. Puts you easily at 250awhp. All be had for under $3,000 too. The K04 moderately built will be around $2,000 either way