as the air becomes cool and slows down it will become turbulent and cause lower exhaust velocities and higher pressures. wrapping your zorst to keep in the heat on an NA car has little effect (though it dose have some)
turbos feed off the heat energy in the exhaust gases. so the difference is more noticeable in turbo cars, especially if it has long primary's before the turbine. after the turbine the exhaust gas pressure will reduce rapidly and causes the exhaust gas to cool. this is why large diameter free flowing exhausts are good after the turbo.
could be wrong, been a while since i did thermodynamics. i remember something about gases been thicker, due to the increased collisions of the gas molecules, at higher temperatures. but as long as the gas flow remains laminar there is no problems, thus the reason we try to keep velocity up. once the air becomes turbulent pressures increases dramatically. Ie after the turbine, so rather then trying to restore the laminar flow of the gases, we try to vent to air asap. this is why the turbo will ideally have nothing but a horn on the turbine exit. But i digress XD
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