Was out and about with window wound down, started to hear a dieselly like noise on acceleration from low revs that disappeared once above 2000rpm. Parked, got back in and turned over easily but not catching. No codes or engine warning light. Has anybody replaced the diesel injector pump in a 2007 A6 C6 Avant 3.0TDI quattro Le Mans? What's involved and likely cost? Is it an exchange item? Motor done 145,000 miles.