last day my passat was over heated and after that it gave loads of smoke on every start i hav changed oil and hav tried smoke treatment but still on cold start it vibrates alot and gives white smoke but after few miles drive vibration goes and smoke vanishes as well.
it was very quiet before over heating with out any smoke.
plz help me and suggest the problem.
thanks

I think your turbo is gone. This was explained in previous posts.