I had a similar issue with my Evolution .46 just today. I thought that being thoroughly broken in by now, that I could lean it out just a bit (only about 3-4 clicks leaner, prob less than 1/8 turn)
Well, the next two times I tried to taxi for takeoff, the engine would rev, and then begin to bog down and lose power.
I reset the needle back to the richer (original) position and things have been fine since...just a thought.
Bob