The obvious symptoms of a faulty coil pack would be:
Poor starting, poor idling, misfiring - leading to poor performance and increased fuel consumption.
Have you checked the spark plugs and have you got fuel pressure ?
If you have the Z22YH engine they have a high pressure fuel pump which can give problems. Also the FPR is worth checking.
Another possibility that causes poor running Is the coolant temperature sensor which controls the fuelling according to engine temp.