I think I found my leak. Some ham fisted moron of a mechanic over tightened the fitting and crushed the o-ring. That dummy figured when using a 27 mm wrench apply the same pressure on the end of the wrench as a 10 mm wrench, and if tight is good, a little more is better. What a dummy. I can't believe I did that.
Anyway, another o-ring from the stack of AC O-rings and all is tight, I think!
It has held 101 PSI for over an hour. I will let it sit for another hour, and if all is good, pull a vacuum. Then recharge with nitrogen, pull a vacuum, recharge to 100 PSI with nitrogen one last time. Then pull a 4 hour vacuum down to 100 microns, with fresh oil in the vacuum pump, and let that sit overnight. If it holds, it will be ready for some refrigerant.
One thing for sure, no professional anywhere would go through all of that, but I want to be 100% positive there is not a speck of moisture hiding as ice in the far reaches of the 40 feet of hoses, 4 condensers, the evaporator and receiver dryer or the other parts of the system.
I is remotely (theoretically) possible I might be a bit anal about it and overdoing it, but is is just nitrogen and electricity and time.