[Lynn Johnson]

You probably have done this, but just in case, check the play you have on primary pump arm. Move the throttle with your hand and notice whether or not the pump arm activates the pump instantly, delivering a squirt of gas into the venturi. If there is any play in this area, a stumble or bog will definitely occur. Same applies to secondary pump, but it is not as noticeable as what occurs on the primary side when you are just starting to move.

Lynn