Which choke would be the best pick using Federal Premium Ultra*Shok number 2 or 4 ammo, for ducks over decoys and pass shooting?

I would say a Mod. tube. I personally shoot a Patternmaster tube in my Super Black Eagle. It is so tight that if it hits them there dead, no wounded birds. But if you are off on your aim that slightest bit your gonna miss um. I found that if the birds are decoying put the bead right on the face and you got them but if they are flying passed you put the bead about an inch in front of there nose and you got him.

last season i shot the federal 3.5" 1 3/8 oz 1550 fps loads, went through about 7 boxes of it. i'm using a briley extended LM tube out of an old style SBE. i liked the results. if you are shooting much #4 shot, you don't need a tight choke. C or IC should be enough. the smaller pellets run out of energy before the bigger ones do if they both have the same muzzle velocity.

I use tungsten-iron out of a modified tube over decoy's.For pass shooting I go with a full choke.

improved on decoy-full when passing