I live in a fairly new house and I find the air pressure is not that high from the vents on the top floor. Is there any way, besides pulling off all of the drywall and taping the joints, or adding another fan, to increase the pressure?
Would just taping the joints in the ducting in the basement make a significant difference?
Where do you live? You can close some of the main floor registers to boost the pressure upstairs. You should have a servicetech check the furnace to make sure the fan is on the correct speed and he may be able to speed it up a bit more. A heat rise test thru the furnace should be done along with the annual maintenance check.