The MAK90 you have is probably 90-94. Actually it definitely is.
It came here with a thumbhole stock. The reason for this was the thumbhole stock allowed them to come into the country with a wide mag well and all the original chinese parts. There are no 922R parts on a stock MAK; The thumbhole stock made it a 'sporting' configuration and immune to the 'compliance parts' of 922R.
The pistol grip on your rifle is the problem here. As soon as it's in that configuration, 922R (Since it's after '89) comes into play. You can only have so many imported parts on a semi-auto rifle with a pistol grip. The Tapco guide above is a good one for what counts and what doesn't. So chances are likely that nobody ever changed out the FCG or floorplates or gas piston for US made ones. Ergo, you're probably illegal under 922R.
That being said, DON'T PANIC. I have never heard of an individual being prosecuted under compliance parts under 922R. More than a few dealers and several importers, yes, but you, no. This is something you can choose to worry about as money for parts comes in.
THAT being said, technically you can have all the pre-1994 'evil' features like your folding stock, bayonet lug, threaded barrel, flash hider, pistol grip. This is the STATE ban we're referring to now. So go ahead and un-pin that stock, thread that barrel, knock yourself out.
ANY magazine prior to the correct date in 1994 is OK, in any rifle of any manufacture date. So don't worry about that.
It sounds to me like you probably have a STATE compliant but FEDERALLY non-compliant rifle. As much as I want to tell you to immediately go get the G2 or G3 trigger group and put it in, I won't, because the MAK triggers are glorious. Take your time, get some other US made stuff, and make it 922R eventually.
If you're still too paranoid, sell it to me and I'll take the burden off your shoulders.
