I did this test - you can see what it was - and it’s not the gaugeset or the vacuum pump hoses, they hold -30 just fine.
Sigh, tmrw I will try to figure out where I messed up. Can I hook my air compressor to the service port and pressurize the system that way? Or should I just redo all the flares? The ones I did were at the outdoor unit when I cut the lines to length, and one flare at the indoor unit end of the liquid line.