Along with the other problems I've been having, excessive oil consumption was a huge issue. Well, Keith at Denver Isuzu is a god! He told me to replace the egr tube, asap! It seems that when this little ditty gets carboned up inside it begins to restrict flow. This pressurizes the crankcase and pushes oil past the rings and pcv valve in minute amounts so it's burned off.
This starts a chain reaction, the more burnt oil in the exhaust the more carbon deposits build and restrict the tube. By the time you start noticing a little exhaust smoke, she's already in trouble and can't breath. He says it's pretty common for 99-02 3.5 blown engines to have a solidly blocked egr tube and an empty crankcase. Every engine replacement gets a new egr tube.
The average person would never link this tube to oil consumption, thinking the pcv system is the problem because that's it's job. A new tube is the easiest way to deal with it, especially if you have over 25k miles and this has never been cleaned out or replaced. Mines not totally blocked, but just enough. My new tube is on order and I'll keep you posted on the results once it's replaced. Hope this helps the rest of you that have been driven nuts trying to solve this and maybe save a few engines out there.