How was the filter? Mine was full of leaves and manky as hell!
I'd recommend this cheap and simple maintainence task to anyone who hasn't already done it!
With regards to the ducting, have a look underneath, behind the dashboard (remove some of the panels for easier access, also the glovebox) and see if the black plastic pipes are all attached firmly (they just slot over one another).
Turn your blower and direct it in different areas and check for air leaks.
Let us know buddy