I wrote an article about the K&N air filters. You will find it in the ENGINE MAINTENANCE section of this board. If you have any questions about the article, please ask.
As for what the B1 code means? It is a maintenance code reminder. A=oil change. B=oil change/brake inspection, 1=Rotation, 2=Replace air/cabin filter...the rest is in the owner’s manual. These codes do not apply to all Honda’s. Best to check your owners manual.