Basically this question is the same as "How do I make a joystick play trackball games?".
You may be able to PLAY Pole Position with the MOMO wheel, but I don't think you'll get it to be really enjoyable.
The places I would start are:
1) Open the joystick config in Windows, and move the wheel very slightly when it asks you to run the "full" range of the joystick axis on it.
This should get it to read "barely left" as "all the way left", and "barely right" as "all the way right".
2) Set the key/joy settings down from what they are now in MAME using the arrow keys to turn.
That should keep the car from hooking right when you hit the "I'm to the right" spot on the stick.
The one downside to this is that releasing the joystick will not bring you back to the left (to go straight), like you would think, it will merely stop the car from turning any farther right.
You will have to pass center, and go left to bring the car back to a straight direction.
This is because the original 360 wheel is set to detect motion, rather than position, like the 270 wheel you are using.
3) Continue to play with the settings until they feel as good as you can get them, and then see if you are OK with them.
My guess is that you won't be, but it might be OK for you.
There really is no substitute for a 360 wheel in 360 games though.
Basically, what you are doing by adjusting the stuff I suggested is turning the 270 wheel into a digital joystick.