If you mean the engine mount and the belt is rubbing on the underside as it goes from the crank pulley to the charger pulley I would check your belt length. It may be too long meaning to tension it you're having to lift the charger too high. Either that or you're over tensioning the belt. It doesn't need to be as tight as the v-belts did.
I know about the ARB mount, got to sort that out too
But yeah, I mean the underside of the engine mount. I have heard these belts can be a few teeth too long, so might go for the 125 tooth belt? I suppose it only needs to be slightly tighter than what the cam belt is, and its not counting on friction to turn the charger over right?
Cheers for all your advice guys, swear rebuilding an engine is never a straight forward job