I don't know what the fuel pressure is supposed to be at, I would just be checking to see if there was a diff. at the diff. levels of fuel. If there is, then I would take it to the tuner and see if he can figure something out with the laptop connected to the truck on a cruise or something. For me it's easy because, I can make a quick call to our GMC dealer we have and they can give me any kind of fuel press. info and such.