Make sure the float bowls were updated. the 03's had a tendancy to starve for fuel on rough trails or jumps. Yamaha updated the bowls with a cup for the main jet to sit in for the 04 model year. Dealers were to replace them, but some guys didn't do it. There were also some other small technical updates between 03 and 04. Your local dealer can probably help you figure that stuff out. I have the technical update manual, if you need more info.
PM me if you need to and I can scan pages or something for you.
Jack
