Jimmy, By your own post title (trouble shooting), I would say you may be close to the culprit being under air cleaner. First: Check all hoses and fittings especially where you hear noise. One way is to get a long piece (arm length) of hose, fuel line size works well, and put one end to your ear and use your other hand to move around area described till you can pinpoint where noise is coming from or visually inspect by taking off all related components (not booster though) and inspect condition, looking for a split or crack. To check your booster, I would use a vacuum pump, like the ones used to suck down an A/C system and see if the booster holds a vacuum.
