The picture is painted, fellas. First of all, the power loss is due primarily to retarded timing caused by carbon chunks all over everything from the manifold flaps to the valve seats. This has been documented in NA. RS4 with 23k miles, no CEL (MIL), no other signs of a problem EXCEPT the timing was around 20 degrees under load (rather than the normal 30 degrees or so with 92 US octane). Owner thought car was fine, but had noted lower top speeds on the straights during track days. Mustang dyno confirmed with 273 WHP and flat curve from 6-8k. Manifold removed to reveal the CB shown above (I presume OP's valves look similar). Valves cleaned, put back on dyno with the same fuel in the tank and intake air temp within 3C of original run. Power went up to 315 WHP and timing was back to normal, with much less retardation. Interestingly enough, this RS4 had used RLI oil from very early on. Its not oil, its not how you drive it, its not the venturi separator and its certainly not coil packs - its simply a by-product of direct injection which is exaggerated on the RS4 by a rather long period of passive overlap.
There were 2 other cases on the same dyno with RS4 owners REGAINING 30WHP+ simply by cleaning the valves. One of those owners was also sure there was no CB on his engine. To my knowledge, the number of RS4's to display CB with their manifolds removed is still 100%. Its not a pretty picture.
