Short stacks = top end
Long stacks = bottom end
Mixing them is a streetable compromise for mid-range, real world riding.
Dude, you are all over the place...like you have some money burning a hole in your pocket, or you spend too much time looking at bikes on FB...I want this, I want that.
Bolt-ons only get you so much...it's a recipe and engine builders aren't going to share their secrets. Compression, cams & head work...that's where the real power gains are and it's expensive. Throwing a few trinkets at it, really isn't going to accomplish much.
It's a slippery slope...how much do you want to invest in a 15yr old 600? There are no returns on this. What do you hope to gain?