Fuel Blowing Out Carb Vent Tubes Under Heavy Throttle: Expert Opinions Please

Carb/fuel system experts diagnosis/opinions please; This is a new problem that just reared its ugly head over a week ago. Stout low 12 second 410 in an A100 van, mild cam, Action+ intake, 750 dp, cold air intake, headers yada yada. Dialed in mostly issue free for over a year. Trying to avoid writing a novel (haha) but what is happening is under either just heavy primary side acceleration or going wot I'm getting fuel spraying out the fuel bowl vent tubes (primaries or both) practically drowning out the motor until I let off, at which ppint the spray/blowing out stops and the motor recovers. This just started one day, drove to work all was fine. On way home went to get on it and this problem cropped up.Took an afternoon with the air cleaner off and test driving to see what was happening. Did this with a dialed in 750 Street Demon (again, with a years worth of mostly trouble free running and drag racing) and is now doing it on recently installed AED 750HOM double pumper. Same issue on both. Been running a Carter 6270 mechanical and a 4594 electrical (at/below fuel tank) with 3/8" hard line, Fram cartridge fuel filter (at/below tank) with Holley 12-803 (no bypass-return) that did fluctuate up and down from a 6psi setting, and at times was showing anywhere from 4 on down to 1.5psi at times. Ditched it the other day for the Holley billet 12-840 (no bypass/return) but got the same fluctuation. Swapped out the cheasy Spectre liquid filled pressure gauge for an old USA made gauge from decades ago, and am getting rock steady 5.5psi at idle, in park holding rpm's at various levels. Checked electric pump output, fuel filter and output through it, up to mech pump, up to regulator, and to carb. All seems good. Still have to road test under load to verify readings. Float levels checked on both carbs, all good. Vent tubes clear, no obstructions etc. Anyone have a clue as to why all of a sudden fuel now sprays out the vents of two different carbs. under primary or wot acceleration, when the pump psi and float levels seem to be good? Tank pressurized, vacuum in tank? Plugged fuel cap vent, issue with either fuel pump? I need to step away and rest my brain, before I end up blowing a gasket! Any insight greatly appreciated:BangHead: