With the A4 they introduced MW-50 injection with the BMW801.
This was keeped till the latest A-Series planes.
But additional boost methods were introduced like GM-1.
Guys, unless you have primary source data, I wouldn't trust it much. MW50 on A4's, and to a certain extent A8's, is most likely the same kind of myth as MG151/15s on 109K4's.
Now, non of us has a primary source that is says it had MW50, nor does anyone have a source that says "MW50 didn't exists on that and that plane but arived FIRST on THAT plane".
As Naudet said, the MW50 was introduced on the A4 (same as the sources i have say), it was somewhat troublesome and wasn't made to work really well untill the A8 arived. The GM1 was even more troublesome and arived at about the same time.
Obviously, the MW50 wasn't used on very many 190's before the A8 thus it shouldn't be modelled for the A5 in AH.
As for the GM1, I see no reason why it should be on an A8. The GM1 didn't kick in untill ABOVE the maximum boost altitude of the engine (this being somewhere around 33-35k for the BWM801D engine if I remember correct). Which means the GM1 is only usefull above that altitude, where, the A8 sucked anyway and didn't fly, nor were there any bombers up that high.
As it is now, I see no proof why it shouldn't have existed in versions prior to the A8, nor do I see any proof that it should. until someone finds a primary source we're stuck where we are. Nor do I think it's a myth like the one Verm is talking about.