When racing, I've never relied on using a temp gun. While I have one and do use it during warm-up laps, during a race, you have to rely on your eyes and ears to know if you are running too rich or lean. If you hear your motor running lean after a few laps, you can pull into the pits without undue damage to the engine.

Some engines will "lean out" from cold to operating temperature (I've had picco engines that (with the same carb adjustment) would be sloppy rich when cold but would be running lean at operating temperature, so you want to adjust your carburetor after it is up to temperature.

With respect to the piccomax 26, I have one in a revo and it is a nice little powerplant. The carburetor is easy to adjust (miniscule adjustments do cause wild swings between lean and rich.