The slight hesitation I had when I asked for extra power disappeared as if by magic, surprised me since the old plugs had only done about 15,000 miles and looked perfect..

Might the act of removing and refitting the plugs, making fresh contact surfaces, have had the same effect ?

Perhaps because I'm not normal people? If thats so, I'll have to try much harder to feel broken up about it.

I'll get on that right away.

Re the standard "Everything from the major manufacturer must be for the best, in the best of all possible worlds" jive, well, yeh, you would think that, wouldn't you, though it aint necessarily always so.

Possible explanations as to why they might not be using them might include those I mention above, i.e. short plug life (commercially a downer) and electrical interference (possibly illegal and quite likely to involve collateral unpleasantness with highly strung computerised cars, like normal people drive.).

Apparently this effect doesn't usually work with resistive low interference plugs, like normal people use.

Some motorcycles spec non-resistive plugs, so I suppose sufficient RF suppression for legality can be achieved by other means but (a) I'm not sure that motorcyclists are normal people. I'd suspect not (in the UK anyway. Here there are so many of them I suppose they must be), and (b) motorcycles tend to use CDI and I'm not sure if this effect is compatible with that.

But I'd have to concede your point that if I wanted b*******, the major manufacturers could supply all my present and future needs, without any need to go poking around on the internyet.

Here's an abstract (all you get without paying) of an SAE (not well known for b*******) paper on it.

www.sae.org/publications/technical-papers/content/.../

They seem to think it has potential for igniting extremely lean-burn mixtures. The use of the phrase "conventional peaking capacitor ignition techniques, which normally employ non-resistor spark plugs" (they apparently get it to work with a resistive plug) might suggest that it isn't as loony fringe as I first thought, simply because I hadn't heard of it,

But then I knew I didn't know everything...I wonder if that's normal?

Whether it makes any real difference in normal running is questionable. Most cars from the 80s onwards have decent electronic ignition systems which can produce a spark of sufficiently high-energy at the right time, and especially with the vogue for individual coils for each plug which is common now.

Certainly its very doubtful that a system not engineered for it, and not using extreme lean burn would benefit detectably.

OTOH, none of the characteristics you list for "most cars from the 80's onwards" apply to mine, which has your classic Kettering points ignition, and so should also be relatively immune to RF interference of electronics, another possible snag.

If I come across appropriate capacitors I might try it, especially If I have the means to examine ignition waveforms. This is probably unlikely, but not completely impossible since there are apparently ways of using a smartphone as a crude oscilloscope.

I don't think I've ever changed the plugs on a car (though I have cleaned and gapped them) because I've never had a problem that seemed likely to be fixed by doing so, and never had the means to measure more subtle improvements that might result.

I have changed them on 2-stroke motorcycles which can get very badly coked-up