Is it castoring nose wheel? We had the same issues on the Rallye for a time - it would always try and turn left. The reason in our case was the left brake was binding slightly and then when you have a left cross wind trying to weathercock the aeroplane to the left, engine effects at power adding to the problems, it was at times almost untaxiable. The Rally is slightly different as the nose wheel is offset to the right of the centreline which compounded the problems. I'd always line up on the runway at about 30 degrees to the right of RW heading so that when I applied full power to start the roll we'd be straight on RW heading by the time the rudder had enough authority.