This started yesterday on the way to work. It is a low volumn high pitched whine that appears to vary in volumn depending on the RPM. Gut tells me it is a vacuum issue and something is acting like the reed on an oboe or something. Verified it is not the door alarm or key in the ignition or lights or anthing.

Anyone seen this before and what was the problem.

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89 190E
2.6L
Arctic white
Grey leather
Sunroof
Pirelli P400 rubber
Smoked corners