yeah, you should just have to clean out the drainage holes. i don't think a canned-duster will work, because there needs to be a LOT of air pressure getting forced into the drainage pipe. what i used was an electric tire pump, with one of the attachments for a beach ball or something it worked, but only when i figured out i had to create a seal around the drainage hole and the pump... if there's some air leaking out, you'll all the pressure.

i think i figured out why my drainage holes kept getting plugged. i used to leave the sun/moon roof open a crack when i parked, for ventilation. well when i park under trees and stuff (which i did a lot), **** would fall in there. ever since i stopped doing that, i haven't had a problem