intermitent hot start problem

[DAWSON-MD]

I have been fighting a hot start problem on with my '87 5Ktq (approaching
200K miles) for about 6 months. It would occasionally fail to start after a
short hot soak of 5-10 minutes such as when getting gas or stopping at a
convenience store. If I let it cool down for about 20-30 minutes it will
start right up as if nothing happened. This would occur about once or twice
a month but now it happens often enough that I avoid turning it off. Last
week I had the unpleasant experience of having to bum a ride the rest of the
way into work from my jerk of a manager after such a failure. He happened to
stop for breakfast at the same place and on the ride in I got a lecture on
buying a proper new "merican" car. Needless to say it is no longer just an
inconvenience. In the past it has always happened under one or more of the
following conditions.

1] it's dark out and I can't see much
2] it's very cold out
3] it's raining / snowing
4] no one is with me to turn the key while I am under the hood
5] no tools with me
6] I am late for work or an appointment
7] all of the above

Two things that I have ALWAYS been able to confirm are that the fuel pump
and relay are working and that there is spark at the coil. Sometimes it will
start after a short wait but will stumble and miss until it "clears it's
throat" and then it will run fine. Once I bump started it down a hill. The
engine was turning over but it didn't hit a lick for about 4 seconds then it
fired right up to a smooth idle. Maybe the vibration of the bump start
jiggled a loose electrical connection or something that was mechanically
bound up due to the hot soak. Today I was able to induce the failure in my
driveway, WOW  light, tools and everything, this should be easy now!. A
timing light shows that the ignition system is working fine, plenty of
spark. Next I checked the airflow sensor disk for sticking and dirt, all was
well. Still no start, it doesn't even hit a lick. I take a break to think
about it and 30 minutes later it starts instantly as if nothing ever
happened. Over the last several months I have been replaced the fuel pump,
fuel filter and fuel injectors. Several times when parking the car I try to
restart it and it always does; but sometimes it won't start 5 minutes
latter. Current theory is that the idle stabilization valve sticks in a
position causing low manifold vacuum (airflow sensor doesn't lift) or the
freq. valve is sticking reducing fuel pressure. This "no start" only happens
intermittently and the car runs great otherwise. Anyone ever experience a
similar problem? Suggestions? (different than my manager's please)
TIA

Mike
'83 UrQ
'84 4Kq
'87 5Ktq
'77 Ferrari 308 GT4