Fobbing or foaming occurs when the liquid is unable to hold the dissolved gas in the liquid any more. What pressure did you use when force carbonating? There are plenty of videos on the web that show you how to make great beer foam fire extinguishers. Most suggest putting 30psi on the keg and then shaking to dissolve the gas . . .reduce to serving pressure and pour lovely foam. . . .
The amount of gas that will dissolve into a liquid is dependant on temperature of the liquid and gas pressure . . . The amount that will remain in the liquid is dependant on turbulence in the serving line, and the pressure differential between the keg and the tap.
For my lager at 10C I set the regulator to 15 psi and leave it for 2 weeks . . .alternatively I set it to 15psi and shake it gently from side to side for 5 minutes . . . I then put it in the Kegereezer for a week to allow it to get to a constant equilibrium. I don't drop the pressure to serve but use 3/16" beer line as this drops the pressure (via resistance) at 3psi per foot . . .so I use 5 feet of 3/16" line between the keg and the tap . . .
Open the tap fully . . . and pour a perfect pint with a good rising bead.
If you only just crack the tap open you create turbulence and gas breaks out of solution causing foam.
If you have overcarbed your beer you may find that it takes a couple of days for the gas to come out of solution . . .leave the pressure release valve open for a couple of days before attaching the gas line and trying to pour a pint . . .cover the keg with a plastic bag.
You may find that 3/8 line is not enough to reduce the pressure for carbonated drinks (IIRC its resistance is something like 0.9psi per foot), and you need to swap to 3/16" . . . What type of tap are you using to serve from as they are all slightly different.
