<VV> Multiple YH Carb Mystery - limited Corvair

[Grant Young]

I am working with a hot rodder who has installed 4 YH carburetors on a GMC blower (435, I think), on top of a SBC, two on each side like was done with the Latham Corvair superchargers. The problem he is having is the same as we have often dealt with on the early YH Spyders - over pressure resulting in leaking out the carb intake, usually at idle or shut down. He has done what I would consider the obvious, including fuel pressure regulation, a fuel return system and tried an individual fuel line set up (1 into 4) and combinations (1 into 2 x 2, etc.). The problem occurs at as low as 2 psi. He has swapped the carbs around and discovered that the problem does not follow an individual carb that might be leaking at one point. The strangest part for me is that sometimes a carb leaks and sometimes in does not, and it never seems to be all 4 at once. I think it probably has something to do with pressure differentials with the blower, but not being even close to an expert on such things, am seeking advice to provide.
Thanks,
Grant
(Recovering from rotator cuff surgery)