Now one thing you half all missed that when a mag fires it has multiple discharge, It is not one spark but several. ...
I don't think that's correct for most standard ignitions on standard GA piston engines. One spark and that's it. I think I've even seen a video of it. Look at the trace at the link in one of my earlier posts. (Of course, there are usually two plugs, each of which usually sparks at nearly the same time.)
... Also you have positive spark and negative sparks, this means that it fires from and to the centre electrode and this gives different wear patens. 4 cly engines a plug will not change per cylinder. Meaning that #1 cly will be a positive spark and #2 will be a negative. Now a 6Cly each time the plug fires it will be different one fire pos and the next will be neg and this gives a more even wear on the plug. ...
Correct. That's why you need to 'rotate' plugs from a positive spark position to a negative spark position.
... Next thing is if you follow the manufacture advice and have you mags and plugs change and serviced you really don't have a problem. ...
True. It's also true that any manufacturer of any product occasionally has quality control problems and produces bad batches.
As for gapping you can gap both types of plugs period.
Yes you can, but you'll likely break iridium fine wires if you do. Ain't no engineer going anywhere near my fine wires with any gapping tool ...
Now depending on the operation of the aircraft what engine it is there are variables to everything . The worse plugs for fouling I've found is training aircraft.
That's probably because training aircraft spend a lot of their time in service at low powers and full rich, such as during taxiing. They should be aggressively leaned on the ground, but most instructors learn and pass on ignorance.
... As for anyone being able to say that they can feel an engine with high gaps I truly find this hard to believe what was the engine ? The only way I know anyone can do that was on the large radial engine s that had oscilloscopes and the really good flight engines could pick which plug it was on a 28 cly, before my time but can remember story's and reading about it as a an apprentice/
Magneto check LOP at altitude will usually be the first indication of degradation, but if you're used to the feel of the specific engine and the usual indications on the engine monitor, you can feel and see it as well.
You can do it the other way around: Collect some plugs with magic resistors that measure high or open resistance on a standard low voltage multimeter. Find an engine that's performing well. Change the plugs with the one's you've collected (after cleaning and gapping). Go fly. (Not my engine, please).
Jabba will probably chip in with his experience.