What fuel octane rating are you guys running in your built briggs engines. When I say built, I'm referring to being higher compression, cam, port work and all the other goodies. Before someone thinks I wanna run racing fuel, I'm not and simply don't have the compression but I think I may need a higher octane fuel. I'm currently running 87 octane fuel.My engine has a steady blue flame out the exhaust and it's not lean, it will make you tear at the eyes. If I lean it out any more than what it is now, the engine will stumble when revved. Timing is set at 30 degrees. Up in the air just debating on trying some 93 octane. I've always ran 87 with no problems and engine is running fine, I just don't like the steady blue flame. My header also started turning cherry red and CHT was at 358 degrees. Any suggestions?