Had a similar problem with mine. I lowered my alternator mounting position 10" to make room for turbo clearance. This left a very long span between the A.C. compressor and alternator. The belt passed VERY close to the water pump belt adjuster/idler pulley on its way by. There were witness marks on top of the A.C. clutch after it tossed a belt. I think it was "flapping" up and down enough to get out of the groove. Solution: I made a small 90 degree guard which is mounted under the water pump idler bracket bolt. It doesn't touch under normal operation, but it keeps the belt from flapping up enough to get out of the groove.