So i have a 97 f150 with 4.6, 4x4, and when i accelerate, or rev the engine, there is a verryy annoying and loud hissing noise that gets progressively louder the more i touch the gas, the noise comes from right under the defroster under the windshield in the center, my heater works perfect, the hoses behind the climate control panels work great, im thinking it may be the small black hose that goes from the engine bay, through the firewall, but have no idea how to check it