With Bosch plugs, right? Sooner or later, you should get those out of your car, and put in some other brand. Get copper of iridium. How were the posts on the coils? Any rust? Make certain that none of the rear wires are touching the O2 sensor. When you replace the O2...stay away from Bosch, also. AC/Delco or Denso only.
The clean up all battery connections, under the back seat. Pay special attention to the bolt that holds the grounding strap to the floor pan. Clean that area, including the threads in the floor real well, and apply dielectric grease. Do the same for the connections under the hood.
Black 2000 SSEi, Silverstar Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, drilled 180 degree thermostat, Intense FWI, PCM, shift kit, and 3.4 Pulley. Solid front mount.