Go get a t fitting and pressure gauge. Put it on each line at the cylinder and see what youe pressure is. If there is a variance then obviously you have an issue upstairs at rhe pump or box. I would be hard pressed to call the cylinder bad. Also, this line you got from another dude. Is it the same size as the one you purchased?
The problem is the gauge will not measure volume. Volume at pressure is key. I would get some plugs/caps and isolate the ram. Then test the box, this will tell you if it is the box or a flow/volume/ram issue
Another idea is call PSC and ask. This is what they do and they should be able to help.
