Yes, it sounds like you definately need a new regulator piston. The older ones weren't set to handle the higher pressures required by the level 10 bolts systems. This can be exaggerated by the barrel that you are using. You can use the shorter gold spring to increase the velocity at a given chamber pressure.
Once you get that fixed, try it to see if it makes a difference with your velocity problem as well. Usually a velocity problem in a classic is caused by a worn regulator seat oring or a level 10 that is not tuned properly. If you have had the valve apart and the regulator seat oring is not new, then you should probably replace it anyway.
Except for the Automag in front, its usually the man behind the equipment that counts.