93 Ford Explorer Stalls While Driving

I have a 1993 Ford Explorer with a 4.0 L that started stalling while
driving about six month ago. It shuts off like someone turned the
key. Originally you could push in the clutch and immediately restart
it without a problem. The occurrence is very random and there is
never anything common between occurrences. It used to happen only one
time during a day until about two weeks ago when it happened twice
within about 10 minutes. It took about 10 minutes each time before it
would restart. Both those times, even though it died like the key was
turned off, it acted like it was out of gas when I was trying to
restart it and then all of the sudden it would start like normal. The
problem seemed to start about the time the vehicle was run extremely
low on gas. Since then the following has been done: fuel filter
replaced, tune-up performed (plugs and wires), fuel pump and EEC
relays replaced, MAF sensor cleaned and the IAC valve inspected. The
service shop where it is taken says there is never an error code in
the system when I bring it in. The vehicle is currently unsafe to
drive with this condition. Any suggestions as to cause and solution
are greatly appreciated.

Thanks,

Rich