Tell me more about your 502. Are you running Q16? If so you don't have near enough compression for it. To run Q or oxygenated fuel you have to richen it by at least 5% or your gonna be WAY LEAN. I run Q16 and LOVE IT!! I went up 5 jet sizes and I was already running over 1600cfm's. The Q fuel isn't gowing to evaporate any quicker it just has more oxygen content which makes it burn faster therefore needs to be richer.
Also tell me about the end of the run. Bumpy, rough track? If so, were you off the throttle when you went over the bumps / bouncing. What I'm getting at is it's easy to bounce around alot and flood a dominator and that's what it sounds like to me by the limited info you gave us.