[whynotthinkwhynot]

Whoa whoa whoa---- I run 103s in my car. No fouling, but I run 87 octane fuel as well. Now if you run a higher octane fuel, ok, you might not need the lower heat range plug to avoid spark knock. In this case, you could see some fouling. I have not seen fouling, and my plug life is more than 20k because that's about when I change them. Now if I'd noticed odd spark plug deposits leaning towards lean, rich, or detonation- I'd have probably switched to something else. On the 104s, I did always see a little big of red indicating high heat. Your performance will be similar to mine since you're on the MS river so probably close to the same elevation. People in higher elevations might not even benefit from colder plugs. Everyone has to do their own experiments- there are so many factors in plug performance, and it's entirely logical that a plug that performs great in one location, won't perform as great in another.