If your timing belt is moving towards your engine and not keeping centered then I would check all of your tensioner bearings as well as your water pump pulley.

A friends MR2 turbo had a issue which due to the water pump pulley having play caused the timing belt to rub against the head.

One other thing.

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if the belt has been reciently changed make sure that there is a washer behind the tensioner pullet which bolts into the head.

Hope this helps

Stuart