So i have a local sign shop with a plant that was working fine and the person working on it a few hours a week got it going again for a while but there's still issues. From what I understand after only seeing it for a few minutes, and what they are saying, is that they can't get the MA meter to go above 2-250 while pumping.

There are no leaks in the manifold nor the units. What they have is a transco system, with a slide choke. I prefer the Variac system best, but have used the slide choke for the past few years. The difference for me is that we have cut pieces of wood for each MM of tubing being used and it works perfectly. Vacuum and everything else is fine and clean (I'm pretty sure).

Wondering if I should try this there for them. Besides trying that, everything was cleaned. What steps should I take to find the problem properly?

Before running the bombarder, give it and the overall electrical installation a good once over.  A cracked insulator bushing will shunt a significant amount of current to ground, limiting what is available to go through the tube.  Also see that the GTO to and from the meter has no excess looped around close to the meter housing....sometimes it is all to simple and tempting in certain layouts to put the excess there when it isn't needed and the field generated will deflect the meter.  Other possibilities can include bad primary connections or--depending upon the incoming service arrangement, even a fault in the contactor or breaker/disconnect switch caused by carbon buildup that creates an added resistance.  

You will want to show up with some test equipment--multimeter, clamp on amp meter, an extra bombarding milliamp meter, etc.  Be prepared to try the different mA meter to rule out a dud in their system and expect to take primary voltage and current measurements with the unit operating,  and also resistance measurements across contacts of breakers, disconnect switches, contactor, etc while the power is off to rule out other  faults.

Chances are you will find the problem in the course of a general inspection and a few basic tests.  If not, feel free to give me a call if you have further questions.