Unless you have Kpro to properly retune for those other inadequate plugs you will suffer many drivability issues.
I have tried coppers and platinums and found they make less power as you have to detune the ignition advance to keep knock under control.
The cost per mile is much much much greater with non-iridium plugs.
There are many who will argue this point and say the coppers and platinums will work fine. But my tests and personall experiences show me otherwise.
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