I've a 2007 octavia  vrs with the pd 170 anda stage 1 remap. 

 

Tonight the car decided to make alot of Vibration that came right through the seat and noise that sounded like a blowing exhaust. I stopped turned of the car then restarted and the problem was gone. Half a hour later and 5 min from home it starts again. Left the car running on the drive to get my overalls and a head torch as it sounds like it's under the car and when I get back the noise has gone again. Any clues. I hate intermittent issues! 

Should also add no codes thrown up and not down on power.