Huma regulator in Marauder F&T

I replaced the Crosmann regulator in my Marauder F&T .177 with the Huma version and the velocity is all over the place. I had a couple of shots in the 930's followed up by one in the mid 500's and then one in the 750's. I also had one over 1400 fps I have the regulator set at 140 bar which is close to where the Crossman was set. I took around 20-25 shots in total. Any suggestions?