I just bought my K5 and have been searching the threads quite a bit. On my maiden voyage in sandy conditions, I heard quite a bit of a knock from the engine. Not use to hearing anything like this, but this is my first K5. I was running 93 octane. I drag race one of my other bikes, so go to the track once in a while where I can buy VP racing fuel. I believe the bike is stock with a gnarly pipe. The guy I bought it from said it still has the same plug in it from when he bought it in '04. What do I need to run in this bad boy as far as fuel? Is octane boost adequate? Hit me with the knowledge! Thanks.