I have a 99, 1500 with the 5.9 I'm not exactly sure when it started but the main vacume hose that plugs into the air filter is SO loud. The ONLY way I can make it stop is to unplugg the PCV valve from the passenger side valve cover. I find it weird when I do this in that the PCV valve is sucking air, & So is the valve cover hole where it plugs into. It seems they cancel each other out but that's the only way the SUPER LOUD sucking stops. Any ideas?