I recently purchased completed RV-8 (quick build kit), 170 hrs TTAF & E, NDH; inspection revealed no obvious problems. Flies like a dream - problem is I intermittently smell fuel fumes in cockpit - this does not occur every flight. This seemingly occurs at random, no particular flight attitude, power setting etc. Although, possibly coincidental, I seem to notice it most often when boost pump is on. There is no visible sign of a leak that I can find thus far, but obvious concern is if I can smell fuel, there are combustible vapors present. Anyone have any ideas about how to chase this down, or what the most likely source would be?