Many of us actually use that very filter and have good performance. I use it in fact. It's pricy from the stealership, but since it is re-usable it will pay for it self.

Same one I use.  I like it.  Same setup as vtail, except that I'm running an Amal Mk2 carb.

When you get your new K&N and take your old stock filter out, I'll give you a buck or so for the old one (and some money to ship it to me even).

I need a spare stock sheet metal frame.

Oldfeller

Even with the stock exhaust in place, you'll see an improvement with the K&N.

Still,  if you don't swap the airfilter, you'll benefit from rejetting and retuning the carb.  All stock, my bike ran it's best with a 55 pilot, 150 main and 2/3 spacer on the needle.

With a cone filter, I went to 1/3 spacer and 152.5 main.

I saw the biggest improvement in my initial acceleration (off the line) as well as power to pass (when already at speed on the expressway.

JFinol wrote on 12/31/69 at 16:00:10:

Look in the Tech Ref forum.  There are several threads and one is specific to carb tuning.  There is even a Table of Contents with most of the threads grouped by topic.