I agree that an IP gauge is needed to address the problem, or at least to ensure that the freeflow is not the result of a worn and leaking HP seat that is causing excessive intermediate pressure.
You can build your own IP gauge pretty inexpensively. You need a run of the mill hardware store or Wal-mart variety air compressor guage (Campbell-Hausfield, etc.), a 1/4 npt to 1/4 npt nipple, a 1/4 npt to low pressure inflator quick disconnect adaptor from your LDS, and some teflon thread tape. The gauge then just plugs into your inflator hose.
Cost should be under $15.00.
If there is any IP creep at all you need to have the first stage rebuilt.
If the IP is solid but the second stage was never properly tuned to the first stage, then you have a couple options for adjustment. If the IP is at the upper end of the normal range (140-145 psi) lowering the IP may be an option as some first stages use an adjustable spring pad and IP can be adjusted externally. On others however, you may need to add or remove shims internally, and that gets a lot more complicated. You also do not want to lower the IP below the 140-145 psi range (with a full tank) if you are workign on an unbalanced piston first stage as IP will drop as tank pressure falls and you do not want to fall below 120 psi on a 500 psi tank.
The easier solution is normally to adjust the second stage to the first stage. There are however both single and dual adjustment designs floating around out there and the procedures for adjusting them are different.
To grossly oversimplify, with a single adjustment design, you normally only need to adjust the deoth of the orifice and the engineering and close tolerances of the rest of the parts ensure the lever will be at the proper height. On dual adjustment second stages you will have to adjust the orifice/seat engagement first, then adjust the lever for the proper height. The specifics very with different designs.
If you are determined to do it your self I would recommend Pete Wolfinger's Book "Regulator Savvy" from Peterbuilt tools (
www.scubatools.com) or Vance Harlows book on reg repair from Airspeed Press.