Well, a couple of things.
1) idle at 600-700rpm, I noticed (looking into the radiator) that the coolant does not flow good. At 800rpm, it was flowing good. So the stock water pump is underpowered at idle. Thus, heater works better while driving.
2) 195* thermostat is factory original. I run it in winter, then run 180* in summer. 15* hotter water makes better heater.
3) air trapped in heater core will not allow good heat. Go here and read.
http://www.supras.com/06/techcenter/...1d623e387fef29
4) if VSV is not working, just remove the vacuum line from engine side and put it on the water valve. This will open it and allow water to flow thru core. The valve is normally open anyway, and only closes when a/c temp is set to coldest position. Valve bad=replace or by-pass it.
5) flaps/doors inside can cause some airflow problems, but....the air that goes thru the heater core is controlled by only 1 door. If it is sending air thru the core, then wherever its coming out (defrost, vent, floor) it should be hot. So if all of the above #'d items are working, then there is a chance that the air if not going thru the core. This problem is hard to work on, as you will need to get into the dash.
http://www.supras.com/06/techcenter/display.php?QID=59