The #5 and #6 TQ plugs are close, but I'm really diggin the #6, which comes with the engine, especially in the 95F+ outside conditions. It allows me to run a tick leaner on the LSN, for a perfect idle, even after pit stops.

The hotter #5 plug was better in cooler conditions or humid night racing. If the #5 is run in hot air conditions you will have to run a richer LSN, which can cause loading-up at extended idle and/or after pit stops. If you don't then it will lean out as your tank gets close to empty, causing a sudden temp surge, resulting in difficult restarts. That's why I've gone back to the #6 for now. We will try to get some #7 plugs on the next factory order.

Has anyone done any back-to-back performance comparisons with an exhaust gas cooler in their return line? I may try one later today.