unleaded gas will leave a black coating in the exhaust pipes. You can’t tell how rich a bike or a car is running by observing the color of the exhaust pipes any more. I am assuming that is what you are basing your rich running on?
So how many Meg’s are you getting. I would run a tank of gas through it and go for a ride, not babying it, but not hotrodding it either, just ride normally. I would think you should be getting somewhere in the range of 43-45. Mpg or so. That is probably more of an indication of running rich or lean.
I don’t understand why people are so concerned about popping in the exhaust on deceleration. I’ve seen many posets about This. When I installed a PC v I got a bit of popping in the exhaust on deceleration but it’s no big deal to me. Most carburetted bikes would not only pop but actually backfire loudly on decel. Fuel injection is a better method of handling fuel, but it’s still not perfect.
I would be very careful about it running too lean. In fact, I think I’d go with the numbers your tuner came up with for optimum. The fuel air ratio numbers from the dyno should be the optimum. If it were my bike, I would go back and tune it, and then get several runs on a tankfuel each, and calculate your MPG. If it’s within a reasonable range, I wouldn’t worry. A lean mixture will make your bike run hotter, impact performance, and so forth.
Just my suggestions. I have never dynoed my bike, as I haven’t found anyone around my area who could do it. I just use a map that was averaged for my bikes configuration. It seems to be ok.
I hope this helps.
Cheers