RV's will not blow equal air out of the furnace ducts. There are different ways they run ducting hose or even in the floor with an aluminum duct. If you have FLOOR mounted ducts, the furthest from the furnace may blow more than ones closest due to the air has to go up at a 90 degree angle from the floor duct. The floor ducts at the end of the duct work the air hits the end and then goes up. If you have 4 inch duct hoses, that depends on how they routed them. They sometime use 1.5 inch duct hose going to a bath area to prevent the bathroom from getting too much hot air and making it unbearable in the bathroom. If you have 4 inch duct hose, then check them out to prevent bunching up. Doug