Possibly could be the cabin air filters. I don't think that would restrict air flow 100% however. Previous Answer->This problem would be best handled by a repair shop. This could be very costly to replace parts, just because a friend had the same problem, does not mean it will be the same solution. My 2002 CX does the same - little to no air flow out the vents on heat or cool. Mechanic can't find anything wrong, not a cabin air filter problem either. Check all the complaints on CarFax - Buick doesn't admit any wrong or manufacturing problem.