I'm not sure which question is being asked.  Regarding the use of "free" ram air, most all airplanes, from C150's to 747's use some feature that attempts to recover the velocity pressure of the engine inlet air.  I think you always want to capture as much of this as practical, regardless of whether the engine is naturally aspirated or supercharged.  The standard 320/360/RV inlet location is pretty good in this regard, being pointed roughly in the direction of air flow and being about the right area.  Does that design add drag?  I'm sure it does, but I doubt if it is even close to negating the benefit from the ram effect.  I suppose the inlet could be somewhere else - some use a flush NACA-type inlet, but I don't know which would result in the best tradeoff.  The second part of the "ram air" question is whether it is worth it to bypass the filter and for this question I say it is seldom worth it.  Most ram air system designs favor the ram air option with regard to restriction, reducing the size of the filter or relegating it to drawing from a heated source without benefit of dynamic pressure recovery.  This makes the "ram air" appear to give a big advantage, when actually it is just eliminating the "badness" of the other inlet path.  You want to use filtered air the most on the ground and less the higher you go - but doing all takeoffs with heated inlet air just to get the filtration is not the kind of thing I would like to do.  Some people take off with unfiltered air, but then why bother installing a filter in the first place?  I propose the best approach is to keep some kind of pressure-recovery inlet and use a full-time large paper filter element.  Then add a blow-in door to bypass the filter if it becomes plugged (happened to me once).  An adequately-sized paper filter will have a pressure drop of only a few inches of water (a foot of water is about an inch of mercury).  I calculated the drop in my system at about 0.1 inches.  Regardless of what you design you still have to make the interface between the cowl and the engine inlet, unless you draw the engine air from the cooling inlets.  That can be done, but there is always a little less recovery there than in a good dedicated inlet.

I designed an inlet for what I thought was maximum ram air recovery and used the largest aircraft filter I could find with an automatic bypass door and I am completely satisfied with the result.  I believe that if you want to use a filter at all the paper variety will offer the best compromise between filtering efficiency and pressure loss.

I think the weakest link in the 320/360 carburetor system is the shape of the transition to the carburetor inlet.  A better design would be worth the effort, in my opinion.

Gary Casey