Code P0302 means more misfires in cylinder #2 than there should be. Yes, it could be due to the coil pack (which you've replaced), but it could also be due to a bad plug (which you've also replaced), or a malfunctioning fuel injector. You could try swapping #2 fuel injector with #1 or #3. Always disconnect the negative battery cable when doing electrical work, and that usually erases the code also. Check to see if the code moves to the new cylinder where the previous #2 injector is now located.
2001 WJ Limited with Quadra-Drive, Kenne Bell Supercharger, 3-inch Kolak exhaust, Stillen rotors (F/R) and MM pads, Addco sway bars (F/R).