every builder does it differnt and calls it differnt.. a lot of them put out nearly drag port cyls and call them "dune port" people for some reason like to say oh man its just a dune port and there is more in it..
my idear of a MX port is pretty involved. infact it to me takes more than a usual "dune port." a TT port would depend on the track style.. short track would take a diff set up then a long track, diff domes, jetting, porting and even pipe choice.. ( at least to me) dunes and drag is easy. make it get out of the hole OK and RIP on top. most dune ports would fatigue a rider a LOT and to be used well in MX applications would take a very strong rider..