Guess I'll have to wait for awhile until a colder plug option becomes available... I do this crazy modification to the plugs that returns better mpg and a tad bit more power. Indexing AND an electrode modfication. But doing it on a turbo four is a bit different. I don't use shims for indexing, I just buy a few extra plugs and find the four I need to get that perfect angle. lol

I used a colder Autolite XP iridium plug in my Mazdaspeed 3 and it ran just fine. XP-5364 is the stock heat range for the Mazdaspeed 3. The stock heat range for our car is Autolite XP-5363 which is the SAME colder option plug for the MS3. By the way, the stock plugs for the MS3 were also FoMoCo plugs, the same as ours just one heat range higher. heh
