At what rpm should turbo start to work, what should gauge read at half throttle.

You need to fill out your signature so we will know what year truck, mods you are running and anything else you have done to your truck. This can vary with modifications and such. With more info we can tell you the info that you are looking for. Normal conditions you should see boost under acceleration and at half throttle will depend on mods. You might see 5-7psi or more and depends on what speed you are talking about too..