[War_Wagon]

You wanted to be convinced why you should leave some things stock. The same thing happens in the drag racing world - people want to go out and reinvent the wheel. But they don't have to, teams of engineers had the 302 motor to work with for decades, and you are getting the benefit of that time/effort/research. Yes they have to make some compromises for mass production, but in general the 5.0L with mass air fuel injection has been pretty much scieneced out already. Stock thermostat gets the engine warmer faster, getting it out of closed loop. Your truck doesn't have a choke, so the computer controls your high idle and mixture when the engine is cold. A colder thermostat means the engine doesn't get to the temperature that the computer is programmed to accept as "normal operating temperature", so it will try to compensate thinkingit can warm up the engine by running richer - just like a choke would make a carbed engine run rich. So a lower temp thermostat is like driving around with a slightly stuck choke.

Electric fans are fine for everyday use, electric water pumps are not. Frank is exactly right, they are made for perfomance applications that are not sitting in traffic, getting used everyday etc. One thing that hasn't been mentioned is underdrive pulleys for the accesory belt. If you want to experiment with how your alternator/power steering/water pump etc effect your FE, check your local craigslist for a set of 5.0L Mustang underdrive pulleys, they should be about $20 for a used set. I would wager that a set of pulleys would make more difference than an air pump delete.