i've got an 08 450f, I installed an Mrd complete exhaust system and took it for a ride, it popped on decel big time and was surging at low speeds or rpm, I jetted the carb accordingly, the popping was gone but the surging was still there, I tried playing with the fuel screw many times, but the problem still exists. I put the stock exhaust back on, re jetted to stock settings to see if the problem still existed, the motor still surges, or "misfires" is more like it feels. The next thing I tried was changing the spark plug, problem still exists. Is there any known problems with misfiring? any help is more than welcome.