If the rear wheel is out of line the car will "crab" rather than pull. So the steering wheel will be slightly off but the car should track straight.
Similalry if the front wheels are OK but the rack is off centre you'll have the same symptom of the steering wheel being off.
If you are having to hold steering lock to go straight then it points to the front wheels being misaligned.
As above, the only adjustment (on the standard car) is via the steering rack so use one of the methods above get the front wheels parallel and work from there.
