i have an 03 passat 1.8 turbo. lately it has been idling poorly, but the engine will run better at speed. it's lacking a little power, so i assume this is most likely a vacuum leak. i have spent considerable time trying to locate the leak and have been unable to do so. this problem started when the weather turned cold. one day last week we had a freak day where the temperature was around 70 degrees. my car ran great. acted as if absolutely nothing was wrong. the next day we were back to cold weather and my car was back to running rough. does this give any clue to the problem? anybody have any ideas?