Is this a commercial keg? That's the impression I'm getting. If it is, I'd recommend you do a few things:
1) Contact the brewery and try to find out the carbonation level in volumes of CO2. If this is impossible, assume 2.6.
2) Use a kegging carbonation
calculator or
chart to determine the appropriate PSI given the keg temperature.
3) Set the regulator to that pressure and leave it there
4) Go to a homebrew shop and buy 10 feet of 3/16" inner diameter vinyl beverage tubing and install that in your system
5) Try pouring. If the first pour is foamy, you may need to solve some temperature stratification problems (copper heat sink, tower cooler, PC fan etc.) or you can live with your first pour of the night being a bit foamy.
If it's homebrew in a corney keg, I'd recommend:
1) pick a carb level for your style, use the calculator or chart to figure out the pressure
2) set the regulator, walk away for 2 weeks except to check the pressure
3) If you're under 3 volumes of CO2, 10 feet of 3/16" ID line should still work
4) After that, if anything but the first pour is foamy, report back and we can help you diagnose further (dip tube o-ring problems, etc)