Well on my 3Ltr Isuzu D-Max (2012) I blanked the EGR at about 40,000Kms. Since then the fuel consumption has increase, maybe 2Km/l. Its considerably worse when driving around Bangkok where the traffic is heavy ... many stop starts and frequent 2-3 minute waits at traffic lights. It appears not to be so bad at higher speeds ... the EGR would be closed anyway then.
The upside is that the oil stays clean! And of course more power at low revs and the car just feels better at those revs.
Even with EGR, a diesel is going to produce more NOx than a gasoline vehicle.
While CO2 emissions have far reaching effects, it doesn't have any local or immediate ones. It also isn't a direct threat to human health. The CO emissions will kill you in an enclosed space before the CO2 ones do. CO2 also didn't close Paris down to diesel traffic over the summer. That was particulates and NOx emissions.
Thats because the government has been taxing fuel and encouraging people to drive low polluting cars for years. Now the downside is that everyone drives a diesel. The upside is that C02 emissions have been slashed. America seems to be the only ones that dont care about C02 unfotunately.
Even with diesels though, my car for example, the C02 emissions are almost 1000% higher than the N0X emissions, and my car is one of the greenest you can get.
NOx will be lower, but it takes less of it to have a negative effect.
The only way to control carbon is to burn less fuel. There is equipment and techniques for limiting other emissions. They tend to work at the expense of fuel efficiency. So it becomes a 'pick your poison'. The Prius could have a better fuel efficiency if Toyota hadn't prioritize emissions.
Prioritize carbon or your wallet over the others, don't complain about the smog in your cities.