Unplug the connector to each coil 1 by 1 until you get no change in how the car idles. That should tell you which cylinder is down. Hopeully its just a bad coil.
Put the timing gun on #1 spark plug wire, have someone rev the motor up and watch the flashes for consitency. Put the timing gun on #2, rev the motor up and watch the flashes for consitency, put the timing gun on #3..... etc.
Thats the first thing id try, but im just a dummy who likes to pretend i have a laser gun.