I think you can get more out of your YS .45 than you are currently seeing. I've seen several turn 11X6's at 15K RPM on 10% Cool Power. You didn't specify which plug you are using or if you are running a stock length header whether it be the pre-tuned system of the full length header. In either case, my first though is you can shorten the header and get even more power out of the engine.

John