Well I guess some of this will forever be interpretational. EGR gasses lower the total volume of combustable gasses in the cylinders. I guess I interpret the fact that these gasses reduce the amount of clean air(combustable oxygen) that can enter the combustion chamber that it is almost the same as richening the combustion mixture since the inert exhaust gasses are lacking in burnable oxygen. That may not be the most acurate analogy. And EGR's are designed to allow an exact amount of flow as well, to much is as bad as too little. I could dump raw fuel down a carb at idle to and it would stall, not because its too lean. I would also like to quote this from a manual..."Carbon monoxide (CO), is incompletely burned fuel or to be more precise are hydrocarbon molecules that split apart but don't burn in the combustion cycle. Hydrocarbons (HC) is simply unburned fuel that escaped the combustion cycle." Sounds like incomplete combustion to me, molecules that are split apart but didn't finish burning. HC is fuel that never even got started. The reality is this guy could pass with just a simple timing adjustment but we can't diagnose that over the internet. But what hasn't been mentioned is that if you look past the EGR as a problem that advanced ignition timing is also a cause for high NOX readings. This guy might just need a timing adjustment or a timing adjustment and a little carb tuning. The possibilities are endless without seeing how the car reacts to any changes. Another funny point is my chart for common emission failures shows a partially restricted exhaust system for both CO and NOX failures. Who knows?