I was driving the other day.. stopped to get gas. Started the truck back up. I have this loud vacum sound now? Coming below or by the exhaust/turbo. Boost is good, sound is there when idl and a little louder until i have boost. the noise goes away? Once i hit 0 psi on the boost gauge the sound is gone? I think i have a vacum leak? What else could it be? Strange thing is it just started i feel for no reason? any ideas? what to look for? thanks