Your not gonna see huge performance gains from going to Iridium. But you most likely will see a gain in electrical/ignition system component lifespan and some better fuel efficiency.
Iridium, per NGK, is mostly a more efficient and lower resistance plug. It requires less voltage to spark, yada yada yada... and in short just means a cleaner, easier, more fuel efficient spark.
For Nos, Forced Induction, wild tweaked drag cars, etc... they have multi surface plugs and colder plugs for most of their product lines. But you dont need and prob dont want those. Just go for either the Delco Rapidfire, NGK Plat, or Zex plugs. I'm about to give the Delco Rapidfires a try. We'll see how I'm feeling this week and or weekend. I have therapy on Thursday, so I should be feeling up to it on Saturday, plus I'll have help on doing it should, or when, I need some.
Good luck, I'll let you know how things turn out with the delco rapidfires. I've used them on several of my track toys and my old 91' Taurus SHO which was mildly modified. Loved the Delco's on that car, very nice plug IMO.
go check these things out @ http://www.iridiumpower.com/default.asp
After reading this, and Zex, and Delco's site I honestly think these Denso Iridiums are the way to go. The Part#/Model# for Legends is IK20, at least it was for the 94' Legend. Anyway, it makes a lot of sense the more I read it. Like I said earlier, it uses less voltage and sparks easier/more efficiently, etc.. so it does seem to be reasonable that they would "increase performance and fuel economy" and all, I'm gonna give my local distributor/speed shop a ring Wed and see what I can find out, esp $$$ wise.
There is some joker on ebay selling these for about every vehicle, but his auctions are kinda hokey to me. I'll shoot him an email anyway to see if the Legend comes with the IK20's or what. His auction says its $70 + $8 for s&h. I'll ask him about doing a group buy option if its for the correct plug for us 2ndG's
I'll let ya know the response.
If you find a local dealer/speed shop with them for less than this, leme know!
The price of $70/set isnt all that bad when you consider how much the NGK's from Acura cost