It would seem that the alignment shop should have taken care of it. It could be that the steering parts are not adjusted properly. This assumes that letting go of the sterring wheel you drive straight. If it pulls to one side, than not only are the steering parts not adjusted properly, but the alignment is off as well.

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1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it