Quote Originally Posted by mmandley View Post

I kept the programmer off my f150 and talked to PHP today. They said for 165 they will reprogram it to a Diesel, give me a new dash mun and include the thermocouple? Whats a thermocouple and where is it located?

Sounds like a good tuning start.
A thermocouple is a temperature sensor that provides data for view or for control. Diesel engines are pretty much governed (the amount of fuel injected) by the amount of heat the cylinder heads experience. So these chips take away the factory settings and let the engines make more power but also more heat but not to the point of damage.