Jukka:
What for that supercharger was need? For better characters on hight altitude, yep?
Il-2 - low level flying aircraft, no need supercharger
Griffon:
As far as I know, there are only FEW designations of that aircraft. Not as in polish monography (there were NO "Il-2type3" or "Il-2M" or other BS).
As far as I know:
Il-2 AM-38 with ShVAK, Il-2 AM-38 with VYa,
Il-2 AM-38 two seater, Il-2 AM-38F two seater, Il-2 AM-38F with NS-37,
Il-2 AM-38F with arrow wing.
Also, as far as I know, in almost all documents there are only two subtypes: Il-2 AM-38 (one- or two seater never described) and Il-2 AM-38F. Thats all.
Yes, Franek:
I have several of his books, and I can say that he is a really best author on Shturmovik subject. He have access to factory documents, archive documents of Il-2 regiments, claims, losses, e.t.c. Photoes, films...