Engine Mechanical problem
1991 BMW 525 6 cyl Two Wheel Drive Manual 174000 miles
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I repaired a crack in the air intake hose (from the filter to the engine and alternator) and now when idling, the car seems to be gasping for air. A 'friend' mechanic i believe adjusted the idle before i repaired the crack. Also, while driving, when i take the car out of gear, i hear a high pitched "rrrrruuuuunnnna na na na". If i put the car back in gear it goes away, it only lasts for a few seconds, but it happens everytime i take the car out of gear or am coasting.

Can you tell us where this noise is emanating from?

a BMW is a fine tuned & unforgiving machine. It sounds like the computer is trying to compensate for any adjustments your "friend" made.You might want to go to a reputable dealer/shop BMW specific and have your mixture recalibrated.