The stock plugs are very good for a stock engine. If you don't mind changing them every 20-30k then the copper NGK TR55s are fine at the factory gap of .035". High compression and forced induction engines need a smaller gap on the spark plugs than the factory gap, as small as .030" for some applications. The new iridium plugs are a good replacement for the platinum stockers but be sure you're sitting down when you see the price.