Engine stutters after timing belt changed

Hi, I drive a 98 ford contour 4dr 2.0l. I just hade the timing belt changed and since then the engine stutters at idle. Almost like its about to stall, but it never does. There is no check engine light and the valve timing is spot on. The tech keeps telling me he has no idea where to start.....So I figure I would do my own homework. Can anyone shed some light on this problem???

Contour.org -> forums.

did you replace the belt or the whole timing system pullies and tensioner?