after a new injection pump install almost 2 years ago, my B4 started to eat the t-belt from the outside edge. MY mechanic noticed it on a routine check and did another belt swap. It started eating from the outside edge as well.
It turned out that after 260K miles, the intermediate shaft bearing was shot and allowing the shaft to be pulled slightly by the belt tension. The belt is running in the center of the pullies now.
The bearing was gone enough that you could rattle the front of the shaft in the hole. Doug at German Performance in Nashville was able to lower the block with the car on the rack and pull the shaft. The bearings were easy with his new tool as featured on these forums.