OK
This is a funny story, I borrowed one of our company cars a Passat LPG/gas car when I crashed my company car (it was a very nice Passat 2012 4 Motion 170 TDI DSG touring with sport package and other stuff, loved that car). the LPG gas car should have been slow as hell but it was a rocket! previous user (a guy that quit at us) must so tuned it... so I was interested to see if it was so when it was time to do maintenance work I asked the dealer to look if it was tuned and they said that they can't see if a VW is tuned. I asked several times but no they refused.
Soo I will service my GTD at the same place, they are very nice so thats not a problem and if they cant see if my car is tuned. Yippie! jackpot! We have strict rule about not tune or company cars. Now I can tune it without any fear =)