i am having a problem with my 45 model 45 when i hit the highway all is well until i go about 40 mph then all of a sudden it dies and the choke knob pulls out by itself. i have replaced all the fuel lines ,installed a new fuel pump, i even took off the fill tube cap thinking it was pulling a vacum in the tank due to poor ventalation. i was wondering if anybody has ran into this problem. i will be driving this truck to a state fire convention in 2 weeks where it will be used for the pumper races so any input will be great because i would like to drive it there instead of trailering it. thank y