Very quick rough test info:
Mk VIII - 18lbs boost, full fuel - 4000fpm+ initial climb, 336mph deck speed
Mk XVI - 18lbs boost, full fuel - 4000fpm+ initial climb, 342mph deck speed
G14 - 1.7atm boost, full fuel - 4000fpm+ initial climb, 345mph deck speed
Spit Mk. V and Seafire now only have peak boost of 12lbs - initial climb rate is around 3000fpm for the Spit and 2750 for the seafire at full fuel!