We have a 1992 Passat, 4cyl, auto. It lack acceleration and has an increasing air hissing noise from the rear of the car as it tries to accelerate. The more you press down on the gas pedal, the louder the air noise. We cannot tell if it is blowing or sucking air. When revving the engine in the parking lot, you hear air leaking near the middle of the vehicle (by the muffler) toward the rear. When accelerating, the RPM jumps higher then 4K after the auto-down shift and the hissing begins. No fuel smell is noted.
Is there possibly a fuel pressure leak? In that whatever is used to pressure the fuel system has a leak in the supply line.
