Do I Need To Test All Of The Spark Plug Wires?
You don't need to test all six spark plugs. Especially since the 3 spark plug wires that face the firewall are hard to get to (actually, they are a complete pain the neck to get to).
To help you get the maximum benefit of this article, I'll go into some detail why you don't have to and under what conditions you would need to test them all:
TEST ONLY 1 SPARK PLUG WIRE
You have a specific misfire code such as: P0301, P302, P0303, P0304, P305, P0306 and you only want to test that specific cylinder
You have already replaced the ignition coil pack, spark plug wires, and the spark plugs with a new ones and you are still getting a specific misfire code lighting up the check engine.
TEST ALL SPARK PLUG WIRES
You have a P0300 misfire code. This code doesn't specify which cylinder is the one misfiring and so you'll need to test them all.
The PCM is not registering any misfire trouble codes to help you find out which cylinder is the one affected (but the engine is misfiring), you'll have to test them all (yeah, I know, life sucks).
If this info really saved the day, buy me a beer!