Why not just remove the cover, leave the filter in place and see if that makes a dif?

 

If you're looking for something that's 'bolt-on', and can use either the OEM or round aftermarket covers, I'm happy with the Ness Big Sucker1 I recently installed on my 93 FLHS. It has a heck of a lot less parts than the Screaming Eagle kit I had installed back in 1994.