I've heard that the previous 2.0FSI(197hp) in the mk5 GTI's are prone to getting carbon build up after a number of miles. Now I'm hearing the 2.0TSI has the same problem. Should I be putting additives in? Should I be worried at all? Also do you HAVE to run premium(91 octane in Canada)? The salesman said the ECU will recognize the grade of fuel (85 at least) and adjust the timing so the engine can run smoothly with downgraded power and efficiency but it may gum up the combustion chamber. Is this true?