what is the other regulator the fuelrail not the fuel presure regulator and what does the screw on the top of it do

 

It is a piece that is supposed to make the fuel delivery to the rail smoother. The screw adjusts the pressure. There is a disk inside it with a spring in there that absorbs pressure spikes so the fuel rail see a smoother pressure delivery...aka, doesn't really do shit lol

 

Ok thanks man very helpful