Re: 75 mm Throttle Body mod
With a super chip, the 75mm may give a little more advantage, however, the heads and exhaust may restrict anything the intake can add. A bigger throttle body allows more air in, competition cams hold the valves open a little further and longer, headers and a bigger exhaust allows the emissions to flow away with less restriction. In old school talk, if you had an 800 cfm carb, but your exhaust would only allow 55 to move freely, the engine would have to work harder to port away the exhaust, so any advantage gained by the intake was taken away by the engine having to work harder to pump out the exhaust. Fuel injection and throttle bodies work the same way.
Prius repellant, just add gas.