I don't know about poor 4000Q heat being normal. I've had three of them
and no problems at all, save the fact that they can go through heater
control cables and control valves. My guess is that if the car gets warm
enough to run properly/ and open even a 160% thermostat and your still not
getting warmth from the heater cores, check for circulation problems before
condemning yourself to a cold winter ride!