I have been thinking about iridium spark plugs for a while, the main benfit that I can see from them is that the resistance for the spark to arc over is WAAAAY less than a conventional spark plug. They seem to help prevent normal misfires and work a lot better under the cylinder stress that our turbos put out. In a supercharged ford expedition at 9 psi there was a gain of almost 30 horses compared to stock oem plugs. That is what you a re buying when you get iridiums. They don't make horsepower they make your ignition far more efficient and help harness the horsepower that you lose due to the lack of efficiency of stock plugs and ignition systems. No matter the price they are one of the best things you can buy for a forced induction vehicle.