I have a possible vacuum leak on my car. I thought that on most or all BMWs when you remove the dipstick or oil filler cap while running, the idle will drop or the engine runs rough.

Is this true on a 95 M50? My idle does not seem to drop. I am trying to track down what I believe are vacuum leaks. After all the car is 10 years old and the PO records did not indicate any repairs in this area. I found the larger hose that connects to the valve cover had a leak. Fixed that and no change in idle.

As usual, TIA.