hi all jumped over from the s3 section hope you dont mind. A good mate of mine has a 2003 rs6 75000miles fsh ever since he has owned it about 3 months it has had a slight misfire at higher revs it was serviced 1000 miles ago and scanned with no fault codes.he took it to the guy who looks after the car[ ex audi tech] he suspected the injector nozzle on number one cylinder was at fault he changed this and still the same. he removed the spark plug and it was very sooty and black all the other plugs are the perfect colour he also carried out a compression test all cylinders where 190 psi apart from no 1 which is 170 he now suspects it could be a cracked or broken piston ring. Do any of you guys think this could be the case has anyone got any other suggestions about what else could be causing this it sound like it could be expensive to fix any help appreciated thanks