Humble Mechanic on Youtube has a few handy vids for Golfs and has a video about checking timing chain tensioner for 2.0tfsi if you want to do it yourself.
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If you know the age of the car and have full log books that show it hasn't been done its probably a safe bet you should get down to your mechanic and get it switched.
I bought my mk6 not long ago and based off this forum got the tensioner replaced immediately. Not the cheapest thing but worth the piece of mind for damn sure.
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