mafs dont care about pressure, they just measure air flow.

our style maf will work as a blow though, although from what i understand after about 2psi they max out voltage wise.

putting the maf before the supercharger means a few things..

its not accurately measuring airflow into the motor, since a supercharger compresses it and heats, then is cooled by the intercooler. the best place to have it is between the intercooler and throttle body, preferably on a straigh piece of pipe, at least 3" before and after the maf.

with a suck through setup, atmospheric blow off valves cause cars to run rich since metered air is begin removed from the intake tract, between shifts... which if bad enough can cause a car to stumble and stall... most blow off valves are atmospheric, and when idling, vacuum pulls them open.. which causes extra air to be ingested by the motor, unmetered, which causes the car to run lean.