Boost only happens in supercharged applications. What he is saying is that unless you do a bunch of mods, or add a supercharger, you don't really need to put in colder plugs or a cooler thermostat. I have an '01 GT with zzp plug wires, a Thrasher intake, colder plugs, and cooler thermostat. Before I added the cooler plugs, plug wires, and thermostat, I was getting 28mpg's on the highway. Now, I get 32 pretty consistently. I'd say that if you plan on doing some other things to your car then you might think about getting a thermostat and colder plugs. Granted, they're cheap enough mods that if you buy them and don't like them you can just take 'em off and you didn't really lose a lot.
That's my 2 cents.
