Chuck, I'd recheck the OVP. The new one I installed temporarily cleared up low idle and stalling, then the problem started returning. I disassembled it and resoldered the board contacts, and no problems in months since.
The issue seems to occur because of an assembly line problem. The internal solder pins are clipped back AFTER soldering, and I think the stress of the clipping physically damages the solder joint integrity. Eventually, the bad contact causes pitting, and operation is erratic. I have seen this in other electronics where this procedure is used.
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7