I installed the K&N Oil impregnated air filter in my LS650. It gave me a noticeable mid to upper RPM power improvement.
Also, I like its seal to the airbox much better than the stock filter.
Beware of the following problems:
1. K&N didn't supply the holding bracket in the box. I had to get the motorcycle shop to pursue K&N for the bracket after having ordered 2 filters. The installation instructions showed the bracket, but it wasn't included in either package. ??? I did finally get the bracket.
2. A couple weeks after installing the filter I noticed the bike would not accelerate normally. Something was hanging up. It might accelerate properly in first gear, but wouldn't in second gear. Sometimes, I would hold the throttle wide open, and something would let loose and the bike would accelerate.
I removed the carburetor and inspected it closely. I found an oily residue on the piston valve and its bore. I cleaned the residue off these surfaces, and normal acceleration was back!
The source of the oil was obviously the K&N filter oil. So, be careful with this filter.
I hope most of the oil has been processed through, and I won't have to take the carburetor apart again.