It does allow greater airflow, assuming you've changed to a freer flowing muffler so that the air filter is actually the bottleneck.  Greater airflow can allow you to get more power out of your bike once you jet/tune properly for that amount of air.  Please note that any freer flowing air filter will allow more particulates into your carb and engine.  However, the K&N still satisfies manufacturers' requirements.  It also allows you to clean and re-oil it instead of replacing it.  I like the K&N and I use it.  I already change my oil more often than required and I'll take that as getting rid of any additional particulates sufficiently.  Just my opinion.

vroom1776 wrote on 12/31/69 at 16:00:06:

Yes.  I am also currently using a K&N drop-in replacement filter, an Amal Mk2 carb and a MAC muffler.

Reelthing wrote on 12/31/69 at 16:00:06:

Well, it took me a bit but I finally looked at it.  Actually, I had to find the Amal jet tool that I'd lost.  I've now ordered a spare.  It's a #290.  I first used a #310 but it was very rich.  Then I ran for a while with a #300 and she ran well but mileage suffered.  Then I went to a #290 and that improved without a noticeable change in performance (sort of like the difference between the #155 and the #152.5 for me on the BS40).  My Amal Mk2 is the 38mm version, if I hadn't clarified that earlier.