The racing plugs from NGK are exceptionally expensive, their standard Iridium plug is great as well. I wouldn't spend the money on the racing plug... I've tracked my car with the standard Iridium plug extensively and had no issues with plug wear etc. I personally feel that the racing plug is just taking more money out of your pocket for no gain/return.
Pros: standard Iridium great, no issues with wear
Cons: racing plugs expensive, no gain/return
Vehicle:
Audi
