Streamline huma regulator And power plenum

Ok put the plenum On every things fine shooting 18 gr at 871 wanted to be around 890 to 900 FPS so I upped the reg to 125 was on 110bar first shot 830 #2 860 #3 970 #4 885 #5 903 #6 912 #7 901#8 876 #9 837 #10 781 so I upped the reg to 140 bar FPS dropped to 588 this is with the hammer spring adjusted from 3 turns in to all in any thoughts or help would be appreciated