Milltek… I actually purchased a used one I got a good deal on when I first got the S6, and then sold it after I did some research.
Milltek, like pretty much all the other tuning companies making S6/S8 v10 stuff a few years ago (prior to JHM getting involved) didnt make anything special for the v10. What they did, was take their C6 4.2 exhaust, and add an extra tip to each muffler, and modify the connecting piece at the other end of the catback. That is it… oh, besides jacking the price up an extra $500 (v10 tax)
Milltek 4.2
https://c1552172.ssl.cf0.rackcdn.com/697637_x800.jpg
Milltek 5.2
https://c1552172.ssl.cf0.rackcdn.com/698635_x600.jpg
Diameter of Milltek 4.2 exhaust 2.36"
Diameter of Milltek 5.2 exhaust 2.36"
Stock the 4.2 A6 makes 335 HP
Stock the 5.2 S6 makes 435 HP (450HP in the S8)
When maximum HP is directly related to exhaust diameter, how is it possible that a v10 5.2 engine, with a similar design, making 30% more HP stock than the 4.2 v8 , would require the same diameter exhaust for optimal performance?
Of course, the answer is it isnt possible. It is just another case of a company selling a product with little, to no, performance gain, a large price tag, and maximum profit due to the fact that they dont have to make any major changes to the 4.2 design, and can just order different mufflers and end pieces.
The non-JHM v10 ECU tunes are the same crap. Very little investment, minimal R&D, (and very little performance gain) in order to maximize profit.
In my experience, I have not seen a single S6/S8 v10 specific aftermarket performance product that I would purchase, that wasn’t made by JHM or the guys making prototype stuff for JHM. And at this stage in the game, with the cars being out for 10 years, I doubt that is going to be any different another decade from now.