07 mustang gt low voltage at idle under load in gear

to start I am now on my 5th alternator they have all started failing one after the other.

1-3rd alternator fried the regulators
1st regulator went out on highway at 65mph
2nd and 3rd at stop light with AC on and headlights on in 1st gear (Automatic Trannsmission)
4th rectifier bridge failed diodes crispy
5th regulator same as 2-3rd scenario

all 5 alternators have been in the last 6 month. orange wire has bat voltage on 3 pin pigtail other 2 have no voltage gencom and genmon labels

Problems do not appear when vehicle is cold only when warmed up
7 am to 7:30 drive to work no problem
4pm on when 85 degrees outside this happens
Load refers to AC headlights and radio
at idle no load out of gear no breaks13.6-14.1v
at idle with load out of gear with breaks13.4-13.6
at idle with load in gear 12.6-12.7
idle load gear and break lights 12.2-12.4

cleaned throttle body(cannot clean iac as sealed to side of throttle body 2007 model) cleaned MAF sensor, checked for vacuum leaks, belt is not slipping, 0/0 gauge ground wire installed between alternator housing and frame, battery to ground wire 8 gauge installed.

when cold idle at stop light in gear with load on idle is 680-720
when warm idle is 550-600 in gear under load during breaking applications