Actually, there are 2. The filter above the axle....and the one at the bottom of the fuel pump assembly inside the tank. Well, its a strainer....but could be looked at as a filter... However, it is not located under the door frame.
What if.......a PO installed a second fuel filter for the substantial HP gain it gives? It's not visible to everybody and it's worth at least 10 stickers, this makes it a sleeper.