Having checked a few gti6 engine's timing belts I have noticed the belt tension is too loose after less than 10,000 miles. All belts were tensioned when fitted using a gauge. I have a theory of why the gti6 engine suffers premature belt failures and why psa went through the cost of revising the design to a 137 tooth spring loaded plastic tensioner. Due to the different cam train loads of the gti6 over the xsi, more strain is put on the timing belt. This combined with the solid metal tensioner causes the belt to suffer excess stretch and results in the timing belt tension being too loose. The resulting belt whip, combined with the cam train tension further lowers the life of the belt. My thought is that the sprung loaded plastic tensioner reduces the belt vibrations and increases the belt life?
It seems most owners prefer the 136 setup due to the metal tensioner? I cannot comment for modified engines, but in the 1000 of various cars I have maintained over the years i have only experienced one pattern plastic tensioner failure due to a manufacturing defect. The other failures have been due to neglect. Most of the manufacturers use plastic sprung loaded tensioner with replacement intervals often exceeding 100,0000 miles.

If people are adamant about sticking with the solid metal tensioner (for modified engines or lack of confidence in plastic) , maybe it's worth looking into having the timing belts checked for tension soon after bedding in and maybe with a view of re-tension if this is the case? Obviously a used belt tension should be less than a new belt tension and I do not recommend tensioning a used belt to new belt settings.

Those who have a lot of experience and knowledge on engines and the gti6 belt flaw, what is your opinions on this?
Has anyone else noticed the tension of gti6 timing belt is less than it should be after little use?

Or people could just change belts every 3 years

I change mine (137 teeth) every 6 years, and is due now again. I only cover 1000 miles per year, and this will be it's 4th cambelt change under my ownership.