OK, no matter what you do to your gun, you will have a post-ban gun. If you have a foregin made gun, you can't have evil features. If you have a US made gun, you can have one evil feature (usually the pistol grip for most people). Since you have a foregin gun now, the way to get the pistol grip is to change it over into a "domestic". That can be done because of the way the law considers a gun to be "foregin" or "domestic". It does this by parts count of certain parts. It's not a total parts count, just the number of forgien parts, and only certain parts, that decide it's fate.
For your gun you would need to replace 6 foregin parts with 6 US parts. These have to be the right parts. Sights, and other BS won't work. There is an official list of parts that count, and only those parts count towards making it a US gun. Once you have the right number of the right parts, you're Maddi is now a US made gun. Presto! You may now have ONE evil feature on your POST-BAN US gun.
It doens't matter when a gun was made or imported. What matters is the configuration of the gun when the AW ban went into effect. As your gun was (is still, actually) in post-ban configuration, and the AW ban has gone into effect, your gun is POST-BAN, and always will be until the AW ban goes away. You can change parts to make it a "domestic" which allows you one evil feature (just like a post-ban AR with a pistol-grip), but you can never make it pre-ban.
Evil features are(for a rifle):
Pistol grip
folding (or telescopic)stock
bayolug
flash hider
grenade launcher
If your gun is "domestic" you get to choose one to have. Obviously things like a folding stock are pretty useless without a pistol grip, but that would be two (one too many) and pretty hard to do otherwise. If you changed enough parts in a Norinco M14s, you could have a flash-hider, but no bayo lug as again that would be two (which is not one).
Your gun is a post-ban. You cannot have any of the above evil features on it. You can have one of the evil features if it's a "domestic". Changing the parts allows your rifle to be "reborn" a domestic and give you ONE evil feature.
DO NOT hesitate to ask further questions about anything you do not understand. I gaurentee others are learning as much as you are from this thread, even though it's "old hat" to many.
Ross