BMW: 84 bmw running rough, air flow meter, vacuum leaks

Question
Josh   I sent a message to you before in reference to my sons car and its problems. I went ahead and replaced the coil (even though it showed good) and replaced the 02 sensor. since this its been running without hesitation....but unfortunately now Ive got a real high idle about 3000 rpms and cant seem to get it down to where it should be.    any suggestions?      sincerely very greatful and loyal fan.

Answer
Tom,
First thing I would check the throttle body, if you cannot find this, have someone move the gas pedal back and fourth until you see where the cable attaches.  This is the Throttle body.  Grab the bracket that the cable attaches to and rotate it.  Make sure that the butterfly is not sticking inside the throttle body.  In other words, make sure that the butterfly will open and close completely.  There is also an idle adjustment screw that should touch this bracket, it is used to manually idle these engines up.  I'm not quite sure why it's there, as Engine management should control Idle, and not by cracking the throttle body open.  Make sure that this screw is not holding the throttle open.  on most vehicles it doesn't touch, but if it is idleing too low, then just screw it back in until its ~750-900rpm (check your manual) it should not take much.   
 It is also possible for you to have a vacuum leak.  There are several rubber boots and hoses that the engine's vacuum is carried though, and if any of them have a leak then it is allowing unmetered air to inter the engine.  Unmetered air is air that has not passed through the Air Flow Meter, and the engine management doesn't know about it.  This air will cause the engine to run lean and usually results in a higher idle.  An easy way to check for vacuum leaks is to start the car and let it idle.  Buy some starter fluid and and spray lightly on any boots or vacuum lines.  If the vacuum line has a leak, it will suck this starting fluid into the engine and you will hear it rev up slightly.  It just takes a small ammount of starting fluid, so just mist it (your not trying to put out a fire).  Check all around the engine for boot leaks and line leaks, and spray a little around the injectors as well.  Injector seals can become old, and allow air to pass beside the injectors.  Once again, if you hear the engine rpms increase slightly, its because it is getting this starting fluid into the combustion chamber.  Find the leak and fix it.  Because Starting fluid is flammable I would go err to the side of caution when spraying it.  I have done this countless times to find leaks and never had any issues.  The starting fluid evaporates in seconds so it's relatively safe.  Just had to include that for safety.
 Thanks Tom, keep me posted on the progres...
 Have a great weekend,
 Josh