Actually, the problem isn't your joystick, it's the game. All the planes are programmed for some pull to the left. This is supposed to simulate "torque" or "gyroscopic procession." The word from real pilots is that it doen't do that well, but it does make the game more interesting.
I believe if you use the regular (instead of advanced or easy) flight model. The pull to the left is turned way down.
"Drew can talk -- by Jove, how the man can talk!" -- James Norman Hall in "High Adventure"