Noticed that too GW.
The last two new air filters, one from a general recreation vehicle supplier and the other from the Honda dealer, did not fit properly in the stock airbox. A comparison with the original factory air filter showed that the new ones were a 1 millimeter or two thicker, metal frame to frame, top to bottom, and also the glued on foam gaskets were thicker and much stiffer and less compressible. These differences wouldn't allow the airbox halves to seal together correctly which left a gap between the airbox halves all around. Removing the new foam gaskets and replacing them with the compressed originals worked for that one.
When installing the second new filter, I noticed small pieces of gravel and sand laying on the bottom of the lower airbox half, after the filter. A straightedge placed inside the lower half on the surface the filter would seat against showed the 30 year old plastic was distorted downward a few millimeters which allowed unfiltered air into the system.
That fix was to leave the top stiff thicker foam gasket was in place, remove the bottom gasket and goop the filter to the airbox bottom with a small continuous bead of silicone. I have not removed this filter yet. Might want to check that too while you're looking.
