SPITFIRE experts- what was a "Gem modification"?

[Wiggy]

Greetings.
Gearing-up to build an "accurate" Mk.XIVc RB188/DL-K.
This ship had the "Gem modification" work completed 5 May 44.
What was involved with this modification? Engine "tweak"?

Many thanks, Wiggy

[MikeHoulder]

Wiggy, can you give a little more context to 'gem mod'?
I doubt very much that it is an engine tweak. More likely it's something like de-sensitising the elevator controls against CG shifts.
Mike

[Wiggy]

Hey Mike, thanks for the responce.
I found-out a "Gem modification" involved tweaking the carb to run "new" 150 octane fuel.

In the hangar, Wiggy