^definately listen to this man. Iridiums are a huge pos in my opinion. When i first got my setup running, I took my car into boost once and the porcelein(sp?) on the plugs cracked and closed the gaps on two of my plugs killing the car. Once i switched to the same heat range NGK copper plugs, my car has run better than ever, with repeated blasts with no signs of a hiccup at all.