Was always told that cooler fuel produces more horsepower and is better efficient. That is why we have the fuel running through coolers on boats. Have you seen this device someone is selling on e-bay Item number: 4406259087. It heats the fuel instead of cooling it and he claims he has a patent that it produces more hp and gives you 200 more miles per tank.

No way. That thing is a piece of $hit. I would love to see it hooked up to an EFI vehicle that runs 60 psi of fuel with those ridiculous hose clamps. How does it hook up to the plastic lines that the factory uses?

Ok, After lurking for a while I FINALLY am making my first post and it's about hot gas!
I won't claim to be an expert however I've been racing for over 20 years now and have my just about worn out my dyno looking for power in all the wrong places. Yes, I would believe that heating the fuel would give slightly more mpg but NO WAY would it give more power unless something was wrong with the engine setup already. You would be begging for detonation. The colder the fuel, the better. I've used my share of dry ice and I know for a fact that the colder you get the fuel (and the intake), the more power you can get out of the motor. I looked over the patent and didn't see any claim of more power however I may have missed it.