Should you GAP new spark plugs?
Spark plugs require a precise gap to ensure proper ignition of the air/fuel mixture, and gapping them requires appropriate tools for your vehicle's specific plugs. Therefore, if your spark plugs need replacing, go out and pick up not only the proper plugs but the tools that will make gapping them easier. via
How do you put spark plugs in a Subaru? (video)
https://www.youtube.com/watch?v=pm5yl6kEjLY
Do NGK plugs come gapped?
While most NGK spark plugs are pre-gapped, there are occasions when the gap requires adjustment. Care must be taken to avoid bending or breaking off the fine-wire electrodes. NGK recommends a round wire-style or pin gauge gap tool to measure the gap. via