The boost port is supposed to store crankcase pressure and release it during a low cycle during scavenging ( exhaust and intake) this is supposed to help bottom end.. but with the newer motors none of them really need it as port and case configuration have made motors scavenge better! I havent seen this used except in the Hyper since around 2002 ish.. seems phased out however it was popular..
as far as the Hyper it might wind a bit farther.. (RPM) but the .28 should by nature have more torque! wich leaves you gearing up as an option.. He should get slightly better mileage but wont be important unless your racing!
as far as adding a boost port its far more work than gain imo.. you wont need bottom end.
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