Re: Cleaning out the carbon
When the engineers designed the head (yes head, not fuel source, not ignition type or anything else - plugs match the head's chamber shape) they designed it around a certain plug - it'll be in the service manual, owners manual, and underhood sticker.
They took in account the heat range, depth, sealing, and indexing when they made their selection.
They also called out torque specs. Torque is important to get the ground electrode in the proper position so it doesn't mask the flame once lit.
The pimple faced kids at the parts house reading advertising hype and lies haven't a clue to what's best for your engine - otherwise they would be the ones designing it instead of working for peanuts.
A misfiring plug may look black, but it doesn't mean rich - just it's not burning all the air/fuel mixture properly. The result is high emissions, poor fuel economy, and worse yet - not getting the use of all the ponies in there.
Think about it -- platinum - it's a better conductor than copper or steel - true. The 1.5" or so of the center electrode may be .00001 ohms lower in resistance - true.
But then why do you feed it with a plug wire with several thousand ohms resistance? It's all in the path of the spark.
Fact - the spark likes to jump from a sharp edge to a sharp edge. But the thin center electrode being smaller has less sharp edge - wears faster, increases required voltage.
Splitfires - the spark only jumps once, and through one path only. That path usually differs slightly each time it fires, but it only takes one path at a time.
Time lapse photography in the splitfire ads show the spark jumping through several paths simultaneously. The photo is actually showing multiple firings, not just one. ANY plug will do the same exact thing -- try it! (Just attach a plug wire to a loose grounded plug and watch the spark jump.) Do you want something in your engine based on a lie?
And - since they don't make very many numbers, "one size fits all." They are a good way to destroy your engine! Do you think they'll pay for a new one?
But all the gimmick plugs get what the maker wants -- your money!!!