The Outerwears prefilter IS the K&N prefilter. They are the same product.
If you buy a K&N it will have Outerwears printed on it (at least they used to), it's just that K&N is selling it to you.
If you didn't change the muffler to an aftermarket unit, you shouldn't have changed the mixture much at all.
Spark plug color is a bit hard to establish. It should be tan to light brown, without any traces of white on the deposits. White means too lean. Use a brand new plug and run it hard for at least 1/2-3/4 mile. Shut it OFF without letting is coast down in speed. In other words, hit the kill switch while running wide open and brake to a fast stop. IF you let is slow down on it's own the plug color with change. Also check it after a normal ride, but here used the kill switch also.
With different gas blends around the country and in different parts of the same
state even, spark plug color is not as reliable of an indicator of mixture as it used to be.
The absolute best way to determine mixture is a ring of brown to gray deposits on the insulator, but this is very difficult to see properly. Take the plug out and look down the insulator with a very strong flashlight. If you see no ring around the plug insulator you are too lean. The closer the ring is to the tip of the plug, the richer you are. Ideally, the ring should be 1/4-1/2" below the tip.
Of course, the easiest way is performance. If the bike runs really good and does not overheat on long strenuous rides, you should be OK.
