So i've noticed a similar anomaly on mine but front to rear rake versus side to side lean. It seems like the rake will adjust about an inch or so for any given reason at times. I've chalked that one up to a full tank of gas in the back on those skinny stock leafs. To a previous post's point, if the fuel tank is inside the frame rails it shouldn't be causing a side to side lean like you're experiencing? Unless the tank is cheated pretty far to one side.