I also came from the LS and Mustang worlds, and you won't find nearly the amount of build-info for the RS6. The market is just too small. Even the the other Audi's (B5S4, etc...) have far more information.

That said, there is still info out there, you just have to dig around a bit for it. First tip: use Google site search to search here. For example try "site:www.rs6.com turbo upgrade" and see what you get.

In general, there are 3 "stages" for the RS6:

(caveat - there are not enough examples to specifically say "do X and Y and get ZZZ horsepower". The numbers I give below are very rough and you can probably find several examples to prove me wrong)


Stage 1: exhaust work and a tune. Stock exhaust is quite good, so just gutting the pre-cats will get you most of the possible power at this stage. You also want to make sure everything is working right on your car too, for example check for leaking intercoolers, MAF's are sealing, plugs/filters are good, etc... I think this stage is good for roughly 400whp (this is very rough, since like mentioned above, we don't have a big database to draw from)

Stage 2: Bolt-on hybrid turbos, fuel injectors, fuel pump, bigger exhaust, bigger intercoolers, meth injection, maybe intake. This stage should get roughly 500whp

Here ends the things you can reasonable do with the stock transmission in place, and even here you'll probably want to explore some of the upgraded transmission options out there. AMD in Seattle is doing some interesting stuff with upgraded internals. To move forward, you'll need to swap to the 6-speed for both physical space and transmission longevity. Also, you are starting to push the limits of the stock rods, although that's definitely open to debate.

Stage 3: Bigger turbos (Tial 605/770/880), Garret GT Eliminator, etc... You'll need at least custom piping for the turbo inlet, and probably custom downpipes. If you really want to get the most out of the turbos, get custom custom tubular manifolds as well. Full 3" exhaust and some sort of custom intake. Probably going to need even bigger fuel pump(s), and might need to put on bigger rails. This is where you want to also take a hard look at building up the block a bit (rods, maybe lower compression pistons, cams, head work, etc...) These setups can push 600-700+ whp, but very few examples of cars like this exist, and the $$$ are getting pretty huge at this point.

Again, there is a lot of good info out there if you spend time poking around, and feel free to ask any other questions!