I have an engine squeal that I have been fighting to get rid of and could use some help.

2004 Mustang GT 223k miles, daily driver, live in Tucson where it is hot
I have replaced myself in the last 2 weeks:
Belt
Belt tensioner
Water pump
Both passive pulleys
AC Clutch assembly
Had a clutch kit installed about 1 year ago, got 8k miles on it.

Squeal:
Only starts after the car is heated up
Is intermittent
Occurs when the AC is either off or on
Gets worse if engine if revved
Occurs in drive or neutral

I have listened with a mechanics stethoscope above and under, but can't localize it. Pored a steady stream of water on the belt with AC off and no change.
Any advice would be appreciated.

Thanks in advance
John