I did have a pair of Piper Cross foam filters fitted but i found that they where far too restrictive and getting sucked in after i had tuned and balanced the carbs, plus screwing the mixture up, so now i am looking into something better. Something with a larger surface area, may even try a stainless mesh fitted to the trumpets to prevent the foam getting sucked in , but its still work in progress as i am waiting for the various types/sizes of mesh to arrive and to see if i can dome the mesh satisfactory enough to do as i intend.
There is a pic of the Piper Cross foam filter fitted in one of my garage pics.
Mike