Well colder air helps too. I mean the principle is the same though, colder combustion chamber = more power. Having a lower temp t-stat causes it to open at a lower temp, and with the cooler water running across the heads that helps to lower the temp inside the CC.
Mike

I have a dream, and that is a 69 Boss 302 with Jules Asner in it.
Current - 2002 Chevy Silverado
Former - 98 SVT E0 T-Red 4/4/97 #173 of 6535(so long girl, you'll be missed)