Help! Car intermittently has almost no power

[Levolorman@aol.com]

Please help with this one (and if any of you have a wiring diagram, that  
would also be helpful)
 
1991 200 Wagon
 
Car runs beautifully...could be for 25 miles or 250 miles, then it acts as  
if it has no power.  if you baby it, you can get it going.  Shut it  off, come 
back 3 hours later (or could be 15 minutes, no telling) and it runs  
beautifully again.
 
My mechanic tells me that his current best guess is an airflow  sensor.  He 
also tells me that the part is $900 (and of course there's no  guarantee that 
he's right).  I already have much too much money into  diagnosing the problem 
with no good results.
 
Do any of you have any thoughts?  Tips? Etc.
 
Thanks
 
Rick Smith
 
JDR Windows  Inc
Providing quality window treatments throughout North  America
914-666-5777 x.13
914-666-5796  (fax)