any ideas on this problem? was towing a trailer with my 01. 5 ctd and running quite good. heard a hissing noise coming from the passenger side of the motor. only made the loud noise when under power. speaking of which, i was wot only going 70mph till i slowed . couldnt see anything upon a quick visual check and the old wiggle check. any ideas. truck is bone stock as it relates to performance modifications. unhooking the trailer did'nt help the power loss or hissing type noise.