I tested the pressure on the 4.0 and it is 31 psi with the vacuum line attached and 40 when it is disconnected, same regulator and same specs for both motors and the reg in my 4.0 test out good. I don't get it.both of my cherokees are running great so I angling to move on to working on my 1st gen Yota, I am working on transforming it into a prerunner. Thanks to all that helped me through this strange ordeal.