I recommend some fat bars. If you ride mx, select a tire suitable for your areas soil conditions. If you ride trails, put a 50 tooth rear sprocket on. The lower gearing will help you in tight stuff and keep your rpms in a manageable range.
The 03 has a known problem, referred to the "notchy clutch syndrome". Not every bike had the problem but there is an easy fix if your bike has not had the repair done. Look at the clutch actuation arm located just above the counter sprocket, if it appears to have been cut and rewelded, then likely the repair has been made. If you are unable to determine if the repair has been made and notice a surging when you let out on the clutch, contact me and I will get you the info for the repair. Parts will cost less than $50. I had the repair done at the dealer for free when I bought the bike new.
I now run the Rekluse Z-Start autoclutch and love it. Click their link on the left side of this page.
You may want to look into the BK mod and the TPS mod. The 'TPS mod is absolutely free and the BK mod might cost you $.05 to $5.00. These two mods really improve throttle response and clean up some flat spots in the power.
One last thing, if you trail ride, this bike is thirsty, check you fuel regularly if you don't like walking for a gas can. I use the Clark 2.3 gal tank.