VWs TDIs have had cooled EGRs since the 1997 model year. Cooler gas = less NOx. Our Passat has 2 EGR circuits, and IIRC 2 coolers

IMHO NOx isn't that big of an issue. Adding a cooled EGR to a 603 probably make a huge difference. The major pollutant on these engines is probably HC and particulate matter.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.