Sounds like the same problem I had on my 95XP. second time it happened I looked closer and found that the back part of the pipe (looks like a can) was suppose to be stapped down, the bracket it was to be strapped to was laying loose in the ski. I rivoted it down and redid the studs, I used 4 studs. Also used locking brass nuts, lock washers, and permanent loctite. I bet you pipe is loose somewhere and this causes it to move around which breaks the bolts.