Reading many good threads here and opinions from those in the know have changed my mind about several mods. that do not appear to be worth the time or effort. The first that comes to mind is a cold air intake along with an oiled filter like K&N. Someone published data showing the efficiency of various filter media that revealed the AC Delco A1618C filter to be superior to all. The next useless mod is a throttle body spacer followed by a lower temp. thermostat. I thank all who posted verifiable data to back their opinion as there is too much hype associated with many of these products. I might add that I fell for most of this on a previous Jeep and will not make the same mistakes. I have no problem spending money on a proven enhancement. .