This may sound odd, but the difference in steering response between right and left may be more a matter of how you control the wheel. It's kind of a subconsious thing, but it's something I picked up on when racing on-road. I spent most of my time at just one track, and got used to a layout that had a few long sweeping left turns and a pile of really tight right turns in the infield. As a result, my wrist became much more used to snapping the wheel hard right. I discovered this when I went to another track and fould that my response going through a quick s-bend was off in one direction.

Also. check the left to right balance of the truck. My pipe sits out furrther because of the long radius header I use. As a result, with the truck on a balancing point it leans a little to the left. As a result, the right rear tire comes up off the ground during hard rights and helps to rotate the truck. If this is the case, just grab a sticky weight like what the electric touring guys use and balance things out.

Sorry if I've sent you on a wild goose chase, but analysing things like these help to win races.

*runs off to find more caffiene*