I suppose it's possible, but I've never seen proof...
There's quite a bit to this subject, but the short and sweet of it is that IF there are any gains to be had they're no greater than you would see if you used NGKs and simply indexed them for optimum ignition.
NGKs are excellent and very reliable; Most of the heavy hitters I know of in the Supra world are still running the OEM specified plugs (although some are running different gaps and/or temps). NGK copper aren't bad either, they need to be replaced more often, but they're inexpensive.
Save your money for other upgrades, there's no power to be made from these.
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