I wouldn't think the egr codes are in anyway related to using WVO, I personally think your going to get them and your going to be replacing egr valves on any diesel that has them on it. And the newer ones are going to be even worse with the 6 egr valves, the epa has mandated stuff that is first inefficient and secondly very costly as well as really doesn't help anything, I drive a semi that has 2 egr valves on it, and at 230,000 miles has already gone through 3egr valves at the cost of $1400 each, and has never seen WVO, and just read a paper that shows that the new 07 emissions trucks the epa mandated changes are expected to raise the annual operating costs by approx $5000-8000 per year, and reduce fuel economy by approx 5-10% thus making us more depend on oil, not less.
The rest of what your saying I would expect, and sounding pretty good so far, keep us informed as thats the only way people find out what is really happening with this stuff.