I just can't figure this one out, maybe someone has some good guidance; My '99 WR400 is "missing" (coughing and spitting) when running down the road at a steady speed, between about 30 and 45 MPH (about 1/4 to 1/2 throttle) most noticably. At lower speeds (and RPMs) and when accelerating up to and over the cruising speeds, it runs like a top. Even when it's missing, if I crack the throttle, it's off like a rocket, but settle back into a steady speed and it starts back up with the missing. It's not real a real steady or cyclic "miss", and I just can't seem to narrow down what it might be. I'm thinking so far it might be a carb issue, but nothing I've done with the carb seems to change the miss. I've gone through the carb (full clean and rebuild) and I'm running good fresh gas. Any thoughts?