While appreciated for the results posted by mrclean it simply points out what we already know. Leaner=hotter, richer=cooler. The important thing to understand is the small amount of time that O2 sensors actually play a roll in fuel metering. Yes, cruising down a highway they do. If they were heated yes they would. But at idle, in traffic, probably not, and this is the condition that people seem to be trying to correct. So, why not go with something that will play a role in all or most conditions. Is it not results we are all looking for? I use a TFI module and it eliminates the O2's. It works great, easy to install, perhaps triple the price but who cares at least it's effective and not partly effective. There are other ways of doing it also, depends how much one wants to spend and whether or not one is going to alter the motor or not.