You might as well upgrade the tensioner pulley to a larger one from either ZZP or wbodystore.com. You can still use your stock sized S/C belt, you'll have a new pulley with new bearings, and you will not need to get a different belt if you drop pulley sizes in the furture down to 3.4" IIRC.

If it still makes the noise after than, then it may be the S/C coupler.