Hi Ernest,  one assumption you make that I will throttle back for cruise, is probably not true.  At least I have seldom done so with my Continental powered Tailwind. I plan to take off full throttle and cruise right around 6000 rpm which is the sweet spot (lowest bearing load) for the 13B.  But your point about the complexity of the switchable intake is well taken.   I prefer the idea of filtered ram air and am going to see I can fit it under the cowl. It is amazing that we have been  able to talk ourselves into supplying unfiltered air at all.  Lot of rationalizing on that one. I am as guilty as anyone else.     BTW,  a few months ago I proposed the filtering ram air  on the other list and was told that filters and ram air did not go together.  I gave it up at that time but here we are again.   Jerry