I bought a new 2004 GMC,it has the LB7 motor. I installed the "Juice" with the "Attitude" monitor. I also have the "AFE" intake and a 4" exhaust (Magna flow). What I immediately noticed is that the "factory guages" do not follow the readings of the "Attitude" monitor. I spoke to the Edge people, and they said that the "Attutude" was far more superior than the factory guage readings. Sometimes the "Attitude" reading will say that my engine temp is 120 and the factory guage will say, like 160 or so. It seems that eventually, after about 30 minutes of driving, the guages seem to catch up. But they don't stay the same. Has anyone else had this observation? How accurate are the factory guages? Especially the transmission guage?

IIRC, 160 is the bottom of the coolant temp gauge. IOW, it won't give you an approximately accurate reading until the coolant reaches 160. I think the gauges probably give you a decent approximation of the temps.

I have a 2003 Chevy with Juice and Attitude and I had noticed the same thing. I guess the factory gauges are just not as accurate. I ran the truck with a GM Tech II unit and the readings were almost the same as the Attitude.