I would add another to the list, and it's a very likely one also.
* Bad tires
I have at times completed a four wheel alignment on a car that has new tires and test drove it only to find it drifted to one side. Everything was in the optimum spec range. I swaped the two front tires from side to side, and then the car drifts the oposite direction. I have had tire dealers tell me that it was not possible for the tires to cause a pull, especially if there was no wear pattern on the tires, but "the proof is in the pudding".
Just a thought,
14 year MB tech
7 year shop foreman @ independent MB/Volvo shop