How does the K04 stand up to the stage 3 kits currently available for the MK6 models?
Stage 3 still trumps. The k04 spools only a couple hundred RPM sooner (250ish) but is down about a solid 20 WHP from 3000 - 5500. After 5500 the K04 starts to die off and power levels drop. The stage 3 keeps going and by redline the stage 3 has another 45-50 whp on top of the k04. This is right in the meat of the power band where you'll be when you're racing.
Also, the stage 3 system is not tapped out. The k04 has a little more room left in it but not much. The stage 3 still has more room left in it.
With later upgrades down the road such as cams the stage 3 will be able to gain even more up top. From there, the stage 3 system also has the added benefit of even more power with possible turbo upgrades and so on. Stage 3+? We'll see! Essentially the system has more room to grow.
Basically, since the stage 3 system spools almost as fast as the k04, the k04 doesn't have a jump on it like it did with the FSI system. both are lightning fast, but the stage 3 trumps it right from the get go.
If I had to choose, I'd go stage 3 on this w/o a doubt.