Interesting read - doesn't mince words about ZD30's

[Plasnart]

Whoa! All seemed well with this article until i got to the end and my BS meter went completely off tap. What can anybody tell me about this "calibrated, pressurised spray of crushed walnut shells" so espoused? Ive never heard of it. Does Nissan offer this service?

There are approved procedures for removing this buildup, most of which use a calibrated, pressurised spray of crushed walnut shells - I kid you not - to abrade off the carbon deposits at periodic intervals.*

Because of this carbon buildup problem there are many after-market suppliers providing blank-off plates for EGR systems. It's a sufficiently sophisticated supply chain to have model-specicifc plates on offer.

Claims made for engines with blanked-off EGR valves include smoother running, improved power and reduced fuel consumption. However, our research indicates that the only measureable benefits are reduced carbon buildup in the inlet manifold and no need to clean the EGR valve periodically.*

Before you blank off your EGR or re-map its operation, bear in mind that it's illegal to do so.