It is hard to figure for a few reasons. Injection gives you less vacuum (restriction) than a carb, and the higher the rpm you build power, the closer the two fuels come. I was told by one engine builder that he could make more power on gas. I never tried it myself, but he is very knowledgeable. In your situation you may see a tenth, maybe as much as three tenths if everything goes in your favor. I gained about a tenth on my switch from Dominator to Terminater, which doubled the airflow at 1.5 inch vacuum. throttle response was impressive. Put it on the bumper the very first pass.