Its very pronounced in the 109s, I've always assumed it was torque modelling. Try taking it straight up like you are roping someone, and then try to roll out to the right. The slower you are, the more rudder you need to make it happen. If you were to realize you were too slow and try to go nose down, its almost impossible to drop the nose to the right in a 109. It will only go left without significant effort. Chopping the throttle (making it similar to a Hammerhead say) makes it easier but its still not as easy as to the left. Even turns to the right are rougher and take more control input to keep steady than turns to the left.