I had the exact same problem with mine, I also have a '01 galant, after many moons trying to find out what the problem was, (hangers, compressed air, pipe cleaners) I found a TSB on this, I dont have the number but the problem is a bad FOAM seal between the evaporator and firewall, they should have used rubber I think, I just pulled the carpet back and globbed silicone around the tube where it goes into the firewall and that fixed the problem. I hope this helps
Wednesday, October 6th, 2010 AT 9:40 PM