If your warhorse of a regulator seems a bit sluggish, give it a bath. It could be the scuba regulator has a buildup of salt deposits from frequent use.
Just grab a bottle of vinegar from the kitchen cabinet and pour a cup or two in a tub of water. Soak the regulator in the diluted mixture for about 10 minutes. Then wash the regulator in warm, soapy water.
If the regulator still is not working well -- or if it leaks -- you may need to take it to your local dive shop or mail it in to the manufacturer for inspection, servicing and repair.