I know mine takes AGES to demist etc, and theres hardly anything come out of the vents. Had a look at the air filter, and mine was just clogged full of oil, road muck etc, probably never been changed ever. Gonna buy a new one, see if it helps. If you're interested, its underneath dash on passenger side. Look for an oblong shape, it pulls off from what I can remember, or there's retaining plastic bolt/pins. Once you have the cap off, the filter will be there.