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Join Date: Jan 2012
Location: Lewisville, NC
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It could be detonating slightly. Our cars have a VERY high compression ratio for a non direct injected motor. The computer will pull timing if you stay in the throttle and the noise will go away. I believe this is happening to cars with higher miles that may be getting some carbon build up in the combustion chamber. This seems to be fairly common on the modern high performance engines like the Audi RS V8's.
You should put in some 100 octane unleaded fuel and see if the noise goes away.
My car has been doing it (wives daily driver) for a little while. I took the car for a few days and ran it very hard (trying to burn off some of the potential deposits) and it appears to be better.
2006 M5 Sapphire Black Metalic, completely stock for now
2001 M3 Red/Blk 6sp, exhaust, coil-overs, and wheels, 19x9.5" with 275/30R19's front and rear
2006 911TT Black/blk 6sp EVOMS GT610 pkg (525whp & 510wtq)