I just did the O ring mod on my YZ426, but I noticed something odd. Even before putting the O ring on, the AP linkage doesn't move very quickly when I chop the throttle. I never had any bog before, but now that the weather is warm I can certainly feel some bog when I chop the throttle. I installed the heavy O-ring that came with the JD jet kit and even with that, it just stretches until the accelerator pump linkage catches up, and the bog is still present when the throttle is opened abruptly. After installing the JD jet kit my bike runs great, however there's a little more backfiring and popping on deceleration than normal. I attempted to install an adjustable fuel screw, however I can't get the existing screw to budge. Are there any tips or tricks to get the fuel screw free?