All good suggestions guys.
EGR is definitely a 2-way street with pros & cons.
It's good for the environment, but has some consequences in diesel engines.
Because EGR lowers the combustion event it also produces higher soot particulates because it's a cooler burn than non EGR engines.
This is one reason why we have DPF exhaust filters now on all 2008 yr model and newer diesels.
EGR can also help with fuel economy, because when egr is active at cruising speeds you have less air entering the engine than a non EGR engine, which is matched with less fuel needed by the PCM.
There is current technology being developed that may replace EGR in the future by means of an ion gas generator integrated onto the engine that produces an a clean inert gas.
Another way to introduce EGR is through valve timing overlap, but I have only seen this in gasoline engines. Valve overlap leaves some exhaust gas in the combustion chamber by retarding the exhaust valve timing. This allows the EGR to be introduced right at the cylinder and keeps it out of the intake manifold.
Being I see EGR related issues daily at my job, it's not entirely problematic. Some vehicles have consistant EGR issues, and some none at all. It's all how the vehicle is being used or driven and the maintenance practices being followed or not that makes some have issues and some not.
Good diesel fuel if available or the use of a fuel additive on a regular basis can help too, especially if you have low grade diesel like we do in my area.
Bio fuels can produce issues like these here...
But thats another story.