Kinda long. Please bear with me... Just want to make sure got all relevent facts. Any advice would be appreciated.

Here's the deal: Car stalls at all speeds on hot days. Had towed home on a 90 degree day. Initially, I suspected bad fuel, but car started and ran fine again when cold. Must wait 10-30 min to cool down, before restart. Sounds like a simple issue addressed in the FAQ. I was wrong...

Reason for suspecting bad fuel at first: A Local fuel retailer (Louisville, KY) recently distrubuted gas w/ too much elemental sulpher and now has to replace hundreds of fuel level senders and some pumps in a 4 county area! Apparently the sulpher is not compatible with some lubricing compounds(I always though it was gas)? Could be a factor?

I had tested several parts and found that if I a put a water hose on the "power stage" ignition amp the car would start instantly and stay running. Tested this theory 3 times before replacing. It always checked out. Also replaced the "crankshaft pos/RPM/reference" sensor for good measure.

Car now seems to stall when hot and coming to a stop or going to idle from higher RPMs. Has not been 90 again (70-80), but car seems to fire up OK and can drive indefinately until next stop. At stop/idle engine hunts from 100-800 RPM quickly, sometimes it will die or will become more stable after 10 seconds. Tested the idle control valve when hot and cold- its motion is always fast and smooth. Since the air temp has been cooler, I am not sure if the problem is the same, better or a completely separate issue...

Known good parts:
idle control valve (tested hot and cold)
temp sensor (matches curve)
Reference/ crank pos sensor (new)
ignition "power stage" amp (new)
wires/rotor/cap/plugs (borrowed from working 700)
Throttle body (cleaned/new gasket)

Unknown:
Fuel pressure reg
Fuel pump relay (can't find- not in fuse box on far left, like 700)
Radio supp relay (can't find- not under hood in ususal locations)
Volt Reg (perhaps voltage dip, not enough voltage to power LH unit- Wild Guess)

Any advice, tips or suspects are welcomed. Thanks in advance!