*bumped*
that egr might be set off by a bad cat, which by the way was probably clogged by leaking coolant from the LIM into your cylinders then out the exhaust... happened to me. I was also getting egr code... new egr didnt help one bit. Hows the power going uphill at 50mph+ ???
once i do a brake job for someone today, I'll be putting the lumina in my garage and tearing down for my 2nd LIM change - first replacement was that same crap plastic gasket as the original. Getting the metal one now its available. Probably tear the heads off to make sure cylinders are ok. sandblast, repaint, probably new lifters and springs.
overheating may be caused by dexcool sludge... is coolant clear?