11.09 @ 120 turning only 5100 is testament to the torque your putting to the ground. 500 more RPM and your running 10.70's at least

I was gonna say the wider 114 509 might work good to overcompensate the head restrictions.

I'd start with fuel, do you have a pressure gauge on it? if you feel it laying down it's likely fuel cause with a blower even with dropping boost it should still pull, just at a lower rate of pull but still harder than say a normally aspirated motor.