I just spent about $165 at the thumpertalk store on a JD jetting kit, a Boyeson Quickshot, and a Zip-Ty fuel screw. I followed the easy to read instructions, and in about 1 1/2 hours my WR426 became NASTY! I also took off the white bros E-2 slip on muffler and replaced it with a used DSP titanium header/muffler that i bought in the thumpertalk classifieds. The throttle response is much quicker, making adjustments with the fuel screw is extra cool. Its like fine tuning in seconds! Here in Florida, the humidity makes a difference on air/fuel mixture and in seconds my bike is syncronized. The mid range power is MUCH better and the power dosnt taper off at high RPM's like before. Instead it keeps on pulling almost to the rev limiter! I do get alot more wheelspin and more un-intentional wheelies. Riding technique will help that issue i think...A very cheap way to nastify you machine!