Thanks for your reply.
In the mean time, I perused site
The Luftwaffe, 1933-45, finding that Bf 109F-4/Z was in use in Africa with JG53, more exactly with III./JG53 and Jabo/JG53, at least from March to June 1942.
Maybe for increase in weight: I've no reliable data about this, but it seems that an increase of 200 kg or so was expected for a single-engined fighter.
I don't think so. According to
this document, GM 1 could be used only above rated altitude (Google translation follows):
"
Use of GM 1.
GM 1 may only be added above full pressure altitude, otherwise the motor will be overloaded and no better flight performance will be achieved.
Minimum operating altitude for aircraft with DB 605 A engine climb 8000 m."
Sure! But would be also nice to have even a single report mentioning an interception performed by this variant. Could be just a curiosity, but I'm intrigued by the high number built: 540 F-4/Z versus 526 F-4 Trop (ref.:
Messerschmitt Bf 109, translation follows):
"
The F-4 version was the most widely used version of the "Friederich", and the F-4 / R1 subvariant appeared (240 examples produced by mid-1942) with sub-wing pods for additional 20mm guns, the F-4 / Z for high altitudes (540 built) and 526 of the F-4 Trop (tropical). In total, the F-4s were produced in 1841 aircraft."
Really? Someone writes that the opposite happened, and that it was Goering who appropriated the name ... However, personally I prefer GM 1, being Italian, since in the Venetian dialect MONA refers to the female sexual organ!