Anyone ever come across their boost gauge whistling with high boost (25 to 35 PSI)? I was pulling a hill today with my 5th wheel in tow and it was around 88 degrees outside, it was at about 1200 EGT and then the boost gauge starts whistling as if it couldn't take the pressure. It changed pitch as the pressure went up and down. It's a 35 PSI gauge. What's even stranger, after I came to a dinner break and started out again, it's not there after pulling another hill about 2 hours later! Anyone? 
