I tried testing with just the tubing (see previous page) and the tubing does bubble in the tank (very slowly) - but I still can't get this to work with ANY diffuser. #2 not working - it's been 45 minutes. I have the pressure at 30.
My apologies, I only skimmed through the last page.
If your regulator is set at 30 PSI delivery pressure (and assuming your needle valve is open wide), and your tubing is only bubbling very slowly into the aquarium, I would look for a leak. Even at 10 PSI, my tubing will bubble very quickly.