That doesn't mean it's right, tho. A little too much toe-in or toe-out will create a nasty ride and wear out the tires really fast. Your car doesn't have to drift one way or the other for the wheel alignment to be off. If you just want to check this for yourself to be sure, here's how:
Firstly, drive the car forward to wherever you're going to do the check and have a buddy make sure you are traveling straight (curbs work GREAT for gauging this, but you can use any good straight line... including one you draw). Essentially you are trying to make sure that the tires are not turned even a little bit. Get a tape measure and mark the very center of the treads on both front tires in two places -the front and the back. Measure the distance between the marks at the front of the tires and then at the back. You should have just a little toe-in (meaning that the front measurement will be shorter than the back measurement). Commonly 1/4" or so of toe-in is normal.
If it weren't for the fact that the problem didn't start until you got the new unit put in, I would suggest that it was a tire developing problems or out of balance, a wheel bearing going out, or a loose/faulty suspension component.