I have had two of them The first one could not be made to work in my gun. The second one, a newer model worked fine. The only improvement is consistency between the shots but this regulator is factory set to 120 bar which is tad too high for our rifles. The pressure is adjustable but for that the cylinder needs to be taken off which in case of the S400f is not difficult but it is a lot of messing about. I also have a second S400 that is not regulated and it is just fine for my HFT needs , about 70 shots around 15 fps spread and about 3~4 fps variance between 165 and 115 bar. I rather work with the unregulated S400, less to tune and worry about.
There are other makes of regulator like the Huma and Lane but these specially the Lane regulator need a lot of post tuning of the gun to get the best of them. Needless to say that the anti tamper has to be removed first.
A.G