Hmm, I always thought that Angels were LOW pressure.
Anyhow, what bottle / regulator have you got ? The make, that is ?
There are two types of preset regulator, HP (About 850PSI) and LP (About 450PSI). Regulators like the PMI or Crossfire ones are usually colour coded, red being HP and blue being LP.
This pressure is the output pressure, I.E. The pressure going into the marker.
Hope that helps.
Edit: Just noticed that you said you have a PMI bottle.
Is it this one:
http://www.planeteclipse.com/site/prodView.asp?prodID=1672 ? I'm pretty sure they are HP only.
You would need to buy a LP regulator, empty your air bottle, unscrew the old regulator and screw the new one on to the specific torque setting. (Hard if you don't know what your doing)
Or you could buy a conversion kit (I think the standard PMI conversion kits for the coloured regulators will work on them regulators) and install that, again draining the bottle before working on it.
Finally you could just buy a LP bottle.
This is all assuming that I can remember correctly that Angels need a LP bottle.
Hope that helps.