Sounds like the regulator needs an adjustment. At the very top of the LP regulator there's a plug (about 1/4" diameter) which can be removed by drilling just under the side of the plug, then using a small punch the plug can be wiggled out. Once removed there's an adjustment screw for the idle circuit.

I will tell you that once I have to start adjusting the regulator that servicing the regulator is in the not to distant future.