Hmm...
When I FIRST got my MOMO wheel (the red/leather one..), it did slightly lean to the left. the drivers at that moment in time were 'revision 4.11'... Not long after, the '4.11c' came out that were supposed to correct this bug. There was also a small utility that could be found on the wingmanteam website. (wingmanteam is the game peripheral division of logitech).
Now, when my wheel is started, it goes pretty much dead-center. But if I don't tilt it full lock left and then right, it's not *really* calibrated. It seems to know its center, but not it's limits.
As an example, I just load Grand Prix Legends and starts running at, say, zandvoort. I go straigth then make a hard right thru Tarzan curve ; when I straighten out my wheel exiting the corner, it's not anymore dead-center. It's in 'weird calibration world'. The next turn will be quite hard for me to apprehend rightly 'cause I won't know how much my input will be boosted/flattened. -- However, if I stop by the side of the road, go lock-to-lock and then start again, I have a very linear steering.
I suggest you go to the wingmanteam website. Have a look through their FAQs (there's a game faq and a peripheral faq), have a look, too, through their drivers and utils. There is a 'beta' section with stuff that isn't usefull to everyone but still can be to you.
Update the driver, if you still have the one that came on the disc.
Good luck!