I would be willing to bet a good amount of that scratchiness was probably the gun being dry where the trigger bar and connector interface. Even new out of the box they're dry and need lubrication, it says so right in the manual. The polishing helps refine the feel and the spring change lightens it up overall. One drop of oil makes a lot of difference.The worst thing about the trigger pull on that thing, was how shitty and scratchy it was, getting to where it breaks. I assume some of your suggested mods would clear that up.