Any opinions, thoughts, views etc appreciated on this before i start spending money chasing an problem. 1999 A6 avant 1.8t, will rev right round to the redline when out of gear and ticking over on the drive. However when driving in 2nd and 3rd gear it won't rev cleanly right up to 6000+. It starts to falter and splutter at about 4500 or so. Initially fault codes showed a fault for a coolant sensor and N85 valve. Both now sorted, faults cleared and haven't returned when checked. No signs of smoke or any signs of turbo giving up the ghost. Pulls fine, drives o.k. nothing else seems untoward or out of sorts. Anyone else had anything similar or any ideas on where i should be looking please ? Want to get it sorted before spending further cash on ecu tune.