Carb fuel filters

I think the mechanicals can pull more than most think. You can boost reference a mechanical fuel pump to upwards of 9 psi plus the 4-5 they put out. IIRC the lever motion of the arm against the eccentric retracts the diaphragm (suction) and the spring pushes it back to give it its constant pressure. If you pressurize the free side (via sealed weep hole) with boost, you are increasing the 'spring' pressure thus increasing the fuel pressure over the stock rating.