I can't remember how long this has been going on but I just had a new Magnaflow cat-back system installed yesterday hoping something might change but nothing has. Still get white smoke on cold starts and accompanied with I believe to be a strong exhaust smell. Also anytime I come to a stop at light or parking lot get a real good whif of strong exhaust. Almost like you are sitting behind a bus or something. I have already had cylinder head replaced and turbo still boosts fine. Coolant level doesn't seem to change. However I have not paid close attention to the color of the coolant, will check tonight. It is possible that the cylinder head has gone again or HG. But every time I mention to mechanic he can never get it to smell. Hoping to take him for a rip tomorrow and see if I can get him to smell / see it. Any advice / experiences would be greatly appreciated. She does have 222,000 km on her too But runs like a champ, no stutters, idles fine, pulls hard and wrecks my buddies S4 B6 4.2 till about 6th gear LOL
Cheers.

 

Sounds like your turbo is tired, have the mech check for shaft play

 

Play on the wastegate?

Cheers