I just bought a new 2002 kdx 220..........there apparently aren't any differences between the two. I put an FMF gnarly pipe and FMF spark arrestor, it's actual name slips my mind right now, but it is wonderful.
I currently have the stock 13 tooth front sprocket, but plan on replacing with a 12 tooth to get a little more low end. Try the pipe first then decide if anything else is needed, would be my suggestion. This is my second kdx, had a 1992 250, when i sold it i voweled to get another, it like a dream come true. I hope you enjoy it as much too.