BMW Repair: car will run then die and wont start, gas millage, vacuum leaks

Question
Hey Josh, thanks for being on this site.
Have a 1988 325 convertable. I recentlty replaced the air intake boot because it was cracked and my car was dying of and on, so I thought that this was going to take car of the problem, but it didn't. The car will start and take me to point A but when I try to start it again it won't start, it will turn over but it won't start. It takes quite a long time to start then I pray I'll make it home. Today I took the plugs out they looked ok, the cap and rotor looked ok too.I turned the car on and played with the accelerator of and on reving it up for about 5 min. then it died and I cuold not get it to start. I'm sure it will start later, but I can not trust it. Is this enough info for you to help me out? I'm driving a 1990 chev suburban right now with the poor gas millage and high gas prices going to work is killing me.
Thanks soooo!!!!!!!! much    Herb

Answer
Herb,
 First I would check to see if the problem is temperature related.  As if the car runs fine when cold, but after 10 minutes it runs bad and wont start/run until it cools off.  If this is the case, I would replace the coolant sensor(s) on top of the thermostat housing.  If this isn't the problem.. see below.
 I would start by checking for vacuum leaks.  You already fixed one (with the intake boot) but there could be more.  Take some starting fluid and spray lightly in several places where there might be vacuum leak.  Around all boots, at the base of the fuel injectors, around any vacuum lines, etc...  If you hear the engine rev slightly, it is sucking in this starting fluid and burning it.  That means you have a leak.  Try to narrow down WHERE the leak is and replace the problem.

 You should probably check/clean the ICV (Idle Control Valve).  Its the little cylinder that attaches to the intake boot you replaced.  Its usually right beside the intake manifold, where the intake boot bends around it.  Take this off, and spray it out with some contact cleaner or carb/choke cleaner.  They get gummed up some times, and cause weird idling.

 If that still hasn't solved the problem, you should look at the Air Flow Meter (AFM).  The AFM is the little silver box-thing on the end of the intake boot you replaced.  It sits right above the air-filter box.  These have a metal contact that rides on an electrically conductive strip, and this strip gets worn out over time, and doesn't send a good signal to the ECU (computer).

 Hope this helps,
 Josh