As Jerry mentioned, there have been numerous "performance" spark plugs on the market (J.C. Whitney used to introduce a "new" one almost every year).
Many of these plugs received "rave" reviews from individuals that actually did receive the increase (since they did a tune-up at the same time as installing the plugs).
As Chuck mentioned, with the CAFE pressure, if they really worked; EVERY new vehicle would come with them. I can never remember any of the manufacturers that even offered any of these so-called performance plugs as an option.
There have been several tests done over the years by third party testers. None of the tests that I have read have showed improvement, and most showed less performance than the more well-known brands.
Jon.
