Just picked up a 2004 Jetta GLS tdi. Its a 5-spd. I noticed when driving it that theres a noise, best described as a high-pitched squealing sound (like air being released from a balloon with the mouth stretched to the sides), whenever your foot is OFF the gas. Once you touch the gas the sound goes away. It sounds like its coming from inside the car, under the pedals. When I was poking around in the engine bay it sounded like it could be coming from the brake booster area, maybe a vacuum leak? Can anyone provide any insight? Thanks guys!