stalling issue other than IAC sensor

I have had stalling issues with my 97 econoline 5.4L gas v8. 105K miles
replaced IAC valve and still occurs, usually on right turns.
runs great, no other issues, then stalls without warning.
need a ford expert advice...

Could be a number of things, you mentioned that it does this on right turns, does it ever do it on left turns. What about with A/C on does it happen more often? Is CEL on? Certain models will have sensor inputs like when power steering is used or A/C is on that will indicate the additional load and PCM will open IAC a little more to keep at desired idle speed. If diconnected or not getting signal from these this could possibly cause your stall problem.
Another thing could be MAF sensor, clean it make sure air filter s clean. Loss of Crank sensor(RPM) input could also be the cause just check and make sure its connected properly, no chaffed wires, etc.
Bad battery connections or engine ground(s).
Too many things could cause your problem best thing to do is just to check one by one of the things a mentioned without being able to look at it its really hard to diagnose an intermitent problem.