I believe the EGR tube is part of the exhaust manifold, so taking it off isn't an option. Chances are your EGR passages in the upper intake manifold are clogged with carbon. Check and fix any vacume hoses that may be cracked/leaking. Pull the intake and throttle body and clean out the gunk that builds up in the EGR passages that run over to the ports in the lower part of the throttle body intake area. (Use carb or throttle body cleaner and a soft rag.) Not sure about removing power from the IAC??? Seems like a strange way to test the EGR. I think most cars will dye with the IAC unplugged. (Idle Air Control) Keep the IAC hooked up and see the effect on the idle when you pump/release the EGR. This cleaning is a common procedure for the V6.
