I think this is the same as arguing about the air resistance caused by the ink of a marker on a PGA Tour pro's golf ball and how it will affect it's flight. For some reason my director found the need to have me admit that yes, there is some form of frictional change empirically speaking. But in terms of affect... Nothing, and not even worth a debate.
Is there a difference? Certainly. Will it make such a difference that switching plugs will ad feelable power? Only if the plugs in it are not right, dirty, obstructed by carbon or ground strap placement, or worn. Meaning you have other issues. In terms of pro racers and OEMs, they use them because of the RFI affects on other systems. Not ignition output. They've had more than enough power for decades now. But they cant have multiplexed circuits getting any RFI from the ignition. Pro cars have almost as many engine monitoring systems as street cars. Dataloggers, ignition systems, fuel pumps, timers, etc. all can be affected by RFI. The radio is irrelevent and most radios will not be affected by plugs alone. Switch to solid core wires and you'll hear the RFI... You can hear it in the cars around you if they have windows down and tunes cranked. A plug is already encased in ceramic insulator and the "leakage" is minor compared to other sources.
