I can think of one potential reason that the G.55 would be 'perked', but it's an odd one.
I can't remember where I read this stuff, but the gist of it is that those G.55s were waiting a long time for German engines.
Now the Italian air force guys were really into acrobatics - moreso than most other air forces of the same era. There are stories of how Italian pilots were against enclosed cockpits because they liked the 'feel' they got from semi enclosed cockpits when they were performing acrobatics. And there are accounts from British pilots fighting against the Italians where the British pilots were commenting on how precise and well coordinated the maneuvers conducted by the Italians were.
In short - they were acrobatic junkies. 8)
Anyways, there was this comparison between the Spitfire and the G.55 done by a British pilot who flew both (it wasn't Brown), and the comparison is not what you would expect. It was a comparison between mass production and hand crafting. Basically, this British pilot said something to the effect of "When the squadron received a new batch of Spitfires, the CO and the XO went out and flew each one. They then kept the 2 best machines for themselves."
His point throughout the writeup was that when aircraft are mass produced, every once in awhile you are going to get an aircraft that is exceptionally well fitted and balanced, and you are going to get some at the other end of the spectrum as well. This difference was apparently noticable and mattered when it came to the combat maneuvering of the aircraft.
He then went on to explain how those G.55s, while waiting for engines and in the possession of an air force known for its love of well handling aircraft, were hand tuned and retuned with balance and other such things checked over and over and over. And because of this, every one of those G.55s was basically a very meticulously hand crafted fighter. They were all real 'hot rods'.
They did pretty good too. I recall an account of U.S. bombers escorted by P-38s running into a small group G.55s and our guys ran into the fight of their lives. I think one of the leading P-38 aces of the war was actually killed in combat with G.55s or MC.205s if memory serves. I'm sure some P-38 psycho can dredge up the details within 2 or 3 minutes of reading this post. 8)
Anyways, with an aircraft like the Ki-84 - you've got 'some' cases where performance was less than test data showed because of poorly manufactured engines.
But in this case you have an entire class of fighter types that got some of their 'ability' from the fact that they were basically hand made.
There are some cool ideas along these lines for perking however. I read about how Spitfires and P-47s often flew with higher octane fuel than they were tested with. Maybe let them fly with a 'higher octane FM' for a couple of perk points from a field that has no damage to fuel facilites. With some of the later war IJN and LW aircraft to get the 'tested' FM you have to pay a couple of perk points (again, from a base with no fuel damage) to fly a Fw 190D using fuel of a quality that didn't exist much in the closing days of WW2.
Just ideas. 8)
But the G.55 by all accounts was a real killer. It never 'made the front pages' probably because by the time it was deployed there wasn't that much time left where the Italian air force was in full blown combat with the Allies. And as a % of total fighters faced by the Allies in the Meditteranean theater it was't that common.
I think alot of people would be in for a shock.
Mike/wulf14 (wulfie of WB infamy)
Future P.R. agent of lazs 8)