If the engine goes rich when the car goes into the slant of the ramp, that means that the engine's getting more fuel pressure. The "G" forces of the transition into the ramp may be forcing fuel to the carb...check the height of the tank and the lines. If the fuel lines can move around, then that may be a factor. Are you getting air agitated into the fuel? That can cause the engine to be lean, and it richens when conditions change, such as going off the ramp...that could change the vibration levels.

You may have the idle a bit too rich, which causes the midrange and acceleration to be a bit rich. That would cause hesitation or stumbling when you come back on the throttle.