NGK BR7EF (3346) copper spark plugs are the ones we use not only for custom tuning sessions but in our own 1000+ rwhp 2007 GT500. They're inexpensive and they work.
We often send them along with tuning devices so our customers don't have to listen to the kid at the parts store tell them that they're not for their car or truck.
Sold in a factory box of 10 so you have a full set plus 2 for replacement as you're checking for signs of detonation (since nobody really trusts the factory knock sensors).
Do NOT use anti-seize with these plugs. They are NOT pre-gapped. We suggest the following:
Up to 15 psi .030
16-19 psi .028
20-22 psi .026
23+ psi .24 or less
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