IMHO... it's a waste of time, money and power.
Most diagrams will show you graphs such as this
Oh, gee, umpteen percent performance increase !
What they don't tell you is that these measurements were taken in a laboratory, where they can "tailor" atospheric parameters to suit their (commercial) requirements.
In the real world, the true air flow will improve (maybe) like this ...
... where most of the time the improvement is negligible ... co$t a lot, nice to look at, but really...
Furthermore, many tests are done on filters such as this
where air is compressed in the "doughnut hole" and throught the filtering material...
...but then they sell you THIS filter in the same box, with the same fancy diagrams, but with actually a completely different aerodynamic response...
What's wrong with this filter ? NOTHING, provided you fit it as part of a system...
...where the plastic shroud acts like a "virtual chamber" where air pressure is made (more or less) equal on all sides of the filter.
Now... imagine fitting such a filter to our Savage, with a "U"-shaped pipe, so that it looks forward.
The plastic "nose" will actually deflect air away from the front part of the filert, creating an area of LOW air pressure, much like what we see when a pickup with a tarpaulin runs at speed and the front part of the tarpaulin will inflate ?
Nevermind the "Trailertail", look at the Orange lines in the nose and "ears" of the truck, that's low air pressure, which makes the tarp swell in the front of the loading bay.
The same happens to a "closed nose" ram air filter
little or no air in the front half of the filter.
It is no wonder that V-Twin professionals at HD give you a good air filter setup as standard, and leave it to the individual to ruin it all...
Harley Davidson OEM setup
GOOD aftermarket airbox
BAD aftermarket airbox