Another thing to look at is are you sure it's the filter? If you valve cover is leaking on the rear corner that's exactly where it will run down to. Very hard to see.
did you by chance buy new valve covers? when I changed my valve covers a few years back...I had drips...found out that 'grooves' in the aluminum covers from the factory or manufacturer , did not seal up with the gaskets...had to add a second gasket , problem solved...
