Ok, here's the issue. My friend has an '01 426. Yosh pipe, boyeson accelerator cover and that's about it. The bike has awesome low end response, great top end but it seems to fall on it's face in the midrange. Say for instance you want to climb a hill, it will start off fine but once you get into the meat of the power it falls off and you have to clutch it to keep it moving. It has been at the local Yamaha dealer twice now but they can't figure anything out. So....I am coming to you guys for help. Our elevation is approx 3200 feet, temps usually around 65-75 for riding. We have half the people saying it is rich and the other half saying it is lean and no one seems to know for sure. Please help me get this figured out. I have always been a 2 stroke guy so this is new territory for me. Thanks for any help.