If the beer lines to each tap are unequal in length, then it will be hard to balance the system. Does the foaming tap have the shortest beer line?
Totally agree. The other thing that could be a problem is foaming until the tap cools down to beer temp. My lines are all the same length but sometimes my IPA's will foam with the first pour until the temperature in the tap equalizes to that of the keg. I serve all my beers at 8 PSI which also helps.
I also notice that the IPA's foam a bit more when I am near the bottom of the keg which is a good indicator that I will finish off the keg shortly.
One other thing. If the keg is over carbonated it will foam, but you already know that. If you still have problems after resolving the other issues, bleed off the head pressure from the keg, remove it from the keezer and rap on it gently with a rubber mallet. That will bring some of the excessive carbonation out of solution (think of what happens when you drop a can of beer and then try to open it right away). You can repeat thee process of bleeding and rapping to remove additional carbonation.