Not too sure about those specific plugs. But as for the gains... not much I would say. I put Bosch Platnium 4's in mine and the others looked like there were right from the factory, so it was a good improvement. However I didn't notice any big performance increase. Maybe 1 or 2 hp... if any.

What I noticed is the responce time. From pedal down to wheels turning time I mean. The old ones were a bit more sluggish, overall it just seemed things were more defined and crisp. But it had pretty much the same amount of power, it seemed, as before.