If the turbo's blowing 20PSI does that double the cfm's? I don't know. Or if that's taken into the calculation.
I don't think I'd want those electric fans in the dirty airstream, seems like nothing but trouble. They'd only be needed at near full load, any lower load and the suction wouldn't matter. The air filter restriction is over rated IMHO, but I don't work on C18's in grinders either. On the stuff I see the air filter restriction indicator rarely trips or even moves, the bigger issue is keeping the filters intact and not leaking dirt into the engine, that will make trouble fast.