I have been able to put a few miles on my 06 Road King after the PC III install and the MPG will average 37 which I figure is a pretty good trade off. Open road and some city miles thrown in not real scientific but that is the best I could tell..I am running M807-225

 

That does sound good for a combo ride.
Mine must not be right then, Last summer had the scoot loaded up, ( read overloaded ) 2 up riding on country roads on a trip through the mountians, and if I did the math right, I got 45mpg. I better read my plugs before I melt something.

 

Do a search and you will find a lot of info on this. Depending where you got your PC III, the map might be a bit rich. I used some of the wisdom here and adjusted my throttle position values in the lower percentages and was able to kick my mpg up. On my '01 RKC with stock headers, SE AC and V&H Basics I was averaging 45 before the PC III, and 36 after. Once I tweaked it a bit I was back up to around 42. Then I went with dresser duals and a new map from Jamie at Fuelmoto and I was down to 35 mpg. I have started tweaking a bit and with one tank through it am at 40. Plugs look fine.