Ok then do this: check the 2 orings that seat the maniforld to the body, check the gasket on the noid. Then check all the orings on the LPR. Replace as needed and relube. Turn your HPR off, then turn your LPR all the way in or on. DO NOT use teflon tape on your LPR this time.
Now turn the air on. and Slowly turn on your HPR untill it reaches 285 fps or starts to leak which ever comes first. If it leaks you will need to turn the air on while the grip frame is off the gun to see exactly where its coming form.
However if its still leaking, then swap out the LPR with one you know for a fact works and try again.
LMK from here, or when you have tried this.