How can you tell if a vehicle has had this done previously? I don't see anything obvious on my truck, but it looks clean so far in the throttle body. (2001 1500 w/~120,000m)

Also, is there any way to tell if the thermostat has been changed to a 180. It looks like on the gauges it stays around 180, but I'm not positive.

 

get one of those long flex magnets at advance, stick it into the throttle body until it touches the plenum? does it stick? if so it still has the factory pan on it. cant think of any ways to tell if the plenum gasket alone or t-stat has been replaced...

 

u can do the pressure test to see if the plenum is leaking