Check Engine light went on on my 2001 TT Quatro. The dealer checked it out and found that the exhaust port on the cylinder head had carbon build-up. They did an induction service to clean it. After completion, the check engine light went on again. Now the dealer wants to charge me $1300 just to pull the head to investigate further. They say I may have additional build-up. Is there something else I can do besides giving the dealer mone $$$?