How much would the following improve efficiency? (20yo gas upflow in the
basement)

1. Make the furnace room airtight and add outside combustion air. This would
eliminate heated air from going up the chimney. There is already CA to the
return but this may not be enough.

2. Turn off pilot when not in use - 8 months/year

3. Increase the speed of blower by changing pulley

4. Set fan Limit switch to start fan sooner and stop later

I know the newer furnaces are 80-96% but I spend $800/yr on gas so the
payback will be too long.