Having a problem with this lift Idling... No Fault codes

I have tried adjusting and cleaning the accelerator pedal potentiometer and throttle body with no change.

Have found if I unhook the hose coming off the intake pipe between the air cleaner and TB it cures the problem. This hose runs off the intake pipe across the top of the engine into a square shaped box that looks like an charcoal canister on a automotive application that is located under the Regulator/Vaporizor assembly. I do not see a sensor in this "box" but on the top of it there is a hose that runs to the LP Regulator/Vaporizer. The thing is this hose doesn't release any pressure or vacuum but if i picks up any vacuum or pressure from either blowing into it or creating vacuum it stalls and dies.. Any ideas to what is creating this problem im having or what that hose and box's Function is?

Thanks in advance help is much appreciated!