Probably too late to do you any good but don't be afraid to modify a tool to make a better tool for the job that needs to be done. You won't find a flare nut tool big enough for the egr nuts but you can make a perfectly servicable one by grinding a notch out of a twelve point box wrench, big enough that you can slip it past the tube. You'll have to shorten the wrench too to get the throw you need so just grind a notch across the handle where you want to break it (were talking a "halfway through" notch) set it on a concrete floor (notch down with a metal dowel propped under the box end) and smack the backside of the notch with a hand sledge. It might take a couple of tries depending on the quality of the steel, but it should snap off. If not, just grind some more or use a cutting wheel if one is available.