a timing light. That's the easiest spot to start. If they didn't line the CAS back up perfectly the timing could be retarded significantly and causing the symptoms you describe.
In addition to that, if you find that the timing is within spec (15 degrees +/- 2 degrees generally) AND you notice that the CAS is rotated all the way over on the adjustment one way or another, you likely have a belt that wasn't installed correctly.