I don't want to over step my boundaries and I may be wrong as I haven't tuned a high hp big blocks but I would check the plugs and if there is no sign of detonation I would start adding timing to the tune up as this will lower the egts. I also think it's a great idea to data log the egt from each cyl. I'm looking into a setup at this time.
If I remember correctly you also had some problems with the old intercooler setup and you now have a new one?, I believe you should be able to lower the intake temps quite a bit with a better properly sized and installed intercooler set up. The reason I say properly installed is because I have seen large differences in temps just by changing the routing of the water lines to straighten them out.
On my old core I thought it was working just fine, then I moved to a larger core with a better lay out and now the temps plummet as soon as I turn on the pump and they stay well under 100 degree's at the end of a run, I have even decreased the amount of ice I run in the tank as the temps can get to cold, the engine really doesn't like below 50* intake temps.
Anyway sorry for he whole intercooler tangent, what I was trying to get at is that if you lower the intake temp you lower the chance of detonation and can increase the timing thereby further lowering the egt.
If I'm wrong please correct me.
Mike Reichen