[Flashman]

Also if you want a mod such as this, Back it up with proof that there was a 25lb's boosted IXe and IXe CW.

After late November 1944 the allies started using 150 Octane fuel in europe (it was in use since march 1944 for some units based in the UK) This 150 Octane fuel allowed ALL Spit IXs (and Spit XVIs) to run at 25lb boost with only a minor modification to the throttle quadrant. Also the SPit XIVs with griffons could run at 21lbs with this fuel

Hence technically all models of Spit IX could/ should have a 25 lb model.

http://www.wwiiaircraftperformance.org/ ... -fuel.html

this link to the aricraft performance website gives a good run down on the use of 150 grade fuel, scroll down to the bit about it entering service with the RAF.