Yes they can, and yes they can, but they don't if you do maintenance. I know i can run Leaner and hit 38, but i will loose Power, it's called trial and error, i tune so that i have the right amount of power when i need it, and i don't need 3mph if i loose 5 at a hill. How do i know when i am at optimal operating temperature? I don't, and i don't care, why should i? i know that i can push it after 1-2 Miles, thats enough.
Why should i run 10° Hotter if i don't gain power with it? I pushed limits, many times, but i don't need a Temp gauge to do so, i don't even know anyone in person that uses them, i can outrun 50cc Motorcycles at a hill with my Supermaxi Cylinders, 1 Gear vs 6 Gears and 8hp.