If the plugs in our R/Ts are indeed copper, the sole "technical" reason for it is that copper plugs are cheaper for the factory to install. Neither the mixture nor the plugs have any idea whether the cam phasing is variable or not. Better plugs cost more. That's why we have cheap plugs. My R/T is option-heavy and a good deal more expensive than the competition, yet it has a piece of wire to hold up the hood, manual HVAC controls, one
power seat, no lights in the glove box or back seat, and a passenger seat that, once released for rear seat access, needs to be readjusted
back into position! These cars are wildly de-contented. I could understand the high prices we're paying for the Challenger if the car was built on an all-new platform, but it's based on a platform that was launched by Mercedes in 2002 and by Chrysler in 2005. If you go to the Dodge website and price comparably-optioned R/T Challengers and R/T Chargers, you'll find that the Chargers are around 2Gs cheaper and better equipped
(the front seats are SRT-type and both are power, automatic HVAC, etc.) for a larger car with four doors! Also, why is an SRT so much more expensive than an R/T? The only things on a base SRT that are more expensive at the factory level than on a base R/T are the intake manifold, the brakes and the seats, and the seats can't be much more as they are used in Charger R/Ts that are cheaper than Challenger R/Ts.
Sorry about the rant. I'm just saying that I'm not surprised that we're stuck with copper plugs...