Ok. Just bought my first Yamaha. 2000 YZF R6. bike fires right up and idle like a champ. As i start down the road. At approximately 4500 rpm. It starts to spudder like its running out of gas and falls on its face. At approximately 6200 rpms. It pulls hard. Pulled the plugs and 1 and 2 are dry. 3 and 4 are wet and dark. The last owner put a K&N filter in it. Supposedly jetted the carbs. Any help would be great. Thanks again for the help.