I concur those shows are usually more infomercial than information, so yes, certainly take it with a grain of salt...or 10-lb bag thereof. You don't know what happens in the footage that was cut or edited that shows all the "tweaking" they did to achieve the end results.
I tried to note the exceptions, but yes, there are many variables that are at work and simply changing to a pricier "super-turbo-triple-platinumized" plug may or may not make a difference. That's why I suggested a more complete ignition upgrade so that there is no weak link in the system...I'm just bad at conveying it in writing. Thanks.