That tech is SO far off it's sad. The Oilheads of that vintage should easily get 40mpg and better. Until I messed with the TPS setting on my RS I never got worse than 40 mpg no matter how hard I rode it. I'd check the O2 sensor, and the TPS voltage setting. If your bike is running that rich though, I'd expect you'd see lots of black soot around the muffler outlet. Mine did that when I had messed with the TPS setting, oh my fuel mileage also dropped to the mid-30's.
Plug color is a reasonble indication. Light medium tan color on the white ceramic portion.