MAF 22680AA240 (leaded fuel) adjustment

[Kiss Me Deadly]

Hi!

I have a donor car from Middle East market. I took off from it and swapped engine+MAF+ECU on my USA market SVX.

Since Middle East market cars has no O2 sensors Im wondering is there any chance to adjust fuel+air mixture?

There is a screw on MAF - look at the picture, what is it for?

Another question - who could explain me whats the difference between MAF with blue sticker and "C" on it (22680aa200) and MAF with yellow sticker and "D" on it (22680aa240)? The same sticker colors are on fuel ramps - blue on my USA car and yellow on my donor car from Middle East.

Thank you.