at idle, disconnecting the vacuum advance should have no effect. double check your float bowls on the out board carbs(this is critical). you will actually want the fuel flowing out pretty good to get it to the right level. then recheck all of the idle adjustments on all 3 carbs with a tach and a vac gauge. what kind of vacuum do you have at idle? a 3.5 power vavle sounds like to low of a value.