I have a 2004 Audi Quattro A4 3.0 with 65,000 miles on it. Recently it started running weird, having problems with power. I took it to an authorized audi mech and he ran diagonstics on it. He told me that the number 5 cylinder's compression is bad. He then said that it was a fairly serious and costly engine problem. Is this a common fault with Audi's or am i just unlucky. Any input is appriciated.