i know. there are no stupid questions, only stupid people...

situation: ranch house w/basement, built 1959, gas furnace in middle of basement.

the supply splits directly above the furnace, one leg along the ceiling into the south crawl space, the other leg towards the north crawl. the leg servicing the north crawl doesn't keep the house hot/cool as the south crawl. the only difference i can see is that the north leg supply plenum drops down immediately after the turn above the furnace to avoid all the plumbing placed in it's path along the ceiling, while the south leg simply performs a 90 degree turn and follows the ceiling towards the crawl. could the fact that one leg performs a more accute angle turn than the other influence the amount of air supplied to it?