as far as i can remember a b20 is primarily a b18, with either a bigger bore, or bigger stroke.

you'd need something big and powerful to suck the exhaust out of a motor. do you know how a combustion engine works?

intake storke
compression stroke
power stroke
exhaust stroke.

the motor uses forces from one stroke to the other help suck in more air, and exhaust more air.

other company's have tried to take the exhaust and pipie it down underneath the piston and have the piston exhaust the gases when it comes down the intake stroke.

turbos/supercharges do not do the "sucking" for the motor. they compress the air so more air gets into the combustion chamber everytime the intake valve opens.