Greetings Environment - 75-80 degrees 600 feet above sea level JD Jet kit 170 main 45 Pilot blue #3 Adjustable fuel screw - about 1 1/2 turns Free mods - fuel screw - air pump, etc. At that point the WR just screamed all the way up top. I installed a YZ pipe and lost my top end completely. Nice low power band and very clean and powerful surge up through the middle but once I'm at the upper RPM range the power goes south and the engine stumbles - seems like lean stumble. Could that YZ pipe make that much of a difference? I'm thinking I'm going to need to start experimenting with the needle position. What is the difference between the red and blue needle - I thought the red needle was for warmer climates.