I was in the mountains in Utah when I noticed my EB was working (running and making the normal hissing sound) but wasn't braking as usual, wasn't slowing me down at all. Normally when stopped the EGTs won't go below 300 while idling with the EB on, now there is very little difference in EGT with the EB on or off. If I had to guess I'd say the valve wasn't closing all the way or is stuck. I't mounted in the middle of the pipe under the truck. Any ideas?