I run a k9 (3 gallons)motor sounds like a dirtbike firing up.motor has a lot of power and just bought another one today,but i do have a question,in the manual that comes with the motor it tells you to add a 0.1 shim if you run 30% nitro through it and it also says that it comes from the factory with 2 headshims but on both of my motors they have 4 shims,does anybody know anything about that?