I used the copper extended tip (I don't remember the part #) recommended to me by NGK tech, as I was in search of a colder plug than the double platinum 6 most of us use on our TTs. Once I hit about 20psi the plugs began to misfire, I immediately put the old platinum 6s back in and the car ran fine at it's normal (at the strip) 24psi. It's my understanding that when you run high boost you want as small an electrode material as possible, that makes the "flame" harder to blow out. I know some members run the copper plugs, but I believe they are using them on stock turbos with 18ish psi. My own experience FWIW. Take care, Mark P.S. I believe you can get the NA plug (which is a shorter reach than the TT plug and is double platinum) in a 7 heat range. I plan to try it myself to bring down the combustion chamber temps. Now I'm done!
