I have a 2005 400ex with white brothers full exhaust and air filter. With a 6sigma jet kit. 42 pilot 162 Main. Did the same thing with 155 main. Problem existed before and after jet kit. The carb is clean, no intake leaks, mixture screw is 2.5 turns out. It starts up and idles fine, when engine in under load of in gear, after 1/4 throttle, it bogs down and wants to die. I don’t know what else to try it’s driving me crazy! Help please any questions I will gladly answer.