the factory oil pressure gauge is accurate (it doesnt "lie" like some people might say the coolant temp gauge does) but its best to get an actual digital "number" reading with the tech 2 or efilive
You can not trust this reading. The Tech2 gets it's info from the same sensor as the factory gauge. If you want a true ready you will go old school and run a mech gauge from one of the oil ports on the block and have a aftermarket mech oil pressure gauge to read