OK, I think we are confusing seperate issue here Russ. Now, hopefully this won't be teaching grandma to suck eggs...
The output pressure from your air source (e.g. geddon, Angel AIR, whatever) needs to be 350psi running out into the vertical reg (front handle) of the A4. Doesn't matter whether your bottle is 3000psi/4500psi, it is the output pressure we are concerned with, not tank pressure.
With that pressure (around 350psi) running into the marker you don't need any volumiser attached.
Run it like that first and see how you like it. The idea of the volumisers is that they allow you to run less pressure into the marker, the bigger the volumiser, the less pressure you have to run in (as there is a greater build up of air pressure in a larger chamber - the volumiser).
It sounds complicated but it isn't.
So, to cut to the chase; don't bother with the volumisers. Put 350 psi into the A4, turn it on = shoot fools
I know it's a balls ache, but seriously read the manual thoroughly, twice - it will save you a lot of headaches when you take it out for the first time