My 92 745T has 211k on it and has developed over the last couple month's a hissing sound the comes from the engine compartment rear passenger side (near the turbo?. The sound only occurs when releasing the throttle in the range of 20 to 35 mph. Is this a vacuum leak somewhere how should I adress this problem. Today I managed to bypass the overdrive solenoid that had been a chronic problem, with some advice from this board, i bent a combination wrench and managed with a breaker bar to pop those bolts off. (sob!!!!!!!!!) 45 minutes later I had my 4th gear back. thanks again for all the great advice. Bigbret