R70 - you answered yourself - they tuned it, put a lighter bonnet on, changed to possibly? lighter wheels, better suspension and better exhaust - how much came from ram air - un-answered. The firehawk was still 200lbs heavier than a c4 though, go figure on the 1/4 times - obviously a better thought out/engineered package.

Not going to knock ram air though, an 1/8th of a psi is an 1/8th of a psi, as stated above the temp difference would be where its at for major performance changes vs under bonnet air

Arguably you would be better off using the cowl air routed to behind the front wheels to help reduce the aero CD