Two questions: 1. What is the adjuster for located at the bottom left side of the FCR39, it has the black plastic knob on it? My manual makes no reference to it whatsoever. 2. At mid-range type RPM's my bike will not run smooth if I try to keep the speed constant, it sputters. So far I've moved my DQR needle clip from position 4 to 3. Based on my searching, I'm considering moving the clip even higher but have not tried it yet. I have a 158 Main and ride at about 5000-9000 feet. Stock uncorked US pipe. Should I try other needles/main jets or can someone recommend some simple adjustements before I go out and start buying jets/needles and the like?