This is the same mechanic your having problems with right? I wouldn't trust anything done by him. Remove all 3 coils, the ICM comes right off then. Make sure the base is clean. The base is the ground for the ICM. Put back together. The bolts holding the coils on need very little torque. Also make sure the plug is clean and drawn in all the way.
Hmm, I had my brother take the car out for a brief highway jaunt yesterday. It still has all the codes and such (I guess the car is also feeling the holiday spirit) and he took it up to 90 and there wasn't any hesitation on the way there. It seems to hesitate solely in city driving. Any ideas?