In my case with the Euro-4 engine i have an electronic EGR valve and a throttle valve.
The Euro-3 had a vacuum EGR and no throttle valve.
The latter was easy, you could just simply remove the whole EGR sh.t and you were done.
Sadly, in my car the ECU is a bit smarter. I also have more sensors then the Euro-3 version. (Manifold pressure and inlet temp behind the turbo)
One of the main differences in EGR control philosophies between the vacuum EGR and the electronic EGR is that the latter is smart.
The vacuum EGR just gets some input to open more and less and that's it.
In my case the EGR valve is used to let the engine warm up more quickly by closing the throttle valve partially to create a vacuum and thus drawing in more exhaust gasses. One way the ECU controls if everything is going ok is to see decreasing flow through the MAF (partially closed throttle valve so less air drawn through MAF). I don't think it's controlled by the vacuum measured by the MAP sensor cause i've already seen vacuums of -150 mbar after the turbo and no errors.
But to continue, if the ECU gives the throttle the command to partially close it expects to see less flow through the MAF. But because i removed the disc from the throttle valve nothing happens with the airflow! So instead of seeing decreasing airflow the MAF keeps seeing the same airflow.
So if, for example, it expects to see 100 ltr/min but it sees 150 ltr/min it generates an error cause for that specific rpm, gas pedal position, temp sensor reading etc the airflow is to high.
In a vacuum EGR system you will never see this error cause the compressed inlet airflow can not be restricted because of the fact it doesn't have a throttle valve. It will only generate this error if there's something wrong with the MAF itself or it's electronics.
In an electronic EGR system the P1030 error can also be generated when the throttle valve will be stuck (will also generate an other error because the throttle valve will send a signal to the ECU if it's open and if the situation is different as expected it will generate an error) but also if some smart asss removes the disc from the throttle valve .
So you didn't misread it, theoretically i can't be getting to much air, a diesel always works with a surplus of air. But because of the programs in the ECU regarding the EGR and throttle valve in my case i can have to much air. Not for real but only in the software.
You don't notice anything when driving it because the engine likes the new situation better but the software doesn't know.
If i want to get rid off it the easy way i will have to get a remap so the software doesn't look at the throttle valve and airflow anymore.
But that will be the last resort.
Simply because i hate to spend so much money for some bits and bytes and i think i can also defeat it mechanical if need be. That's why the first draft was with the EGR valve working with clean air. And i like to improve things if i think i can, if you do it yourself it will be a lot more satisfactory
If the ECU isn't capable of adapting to the new situation i already have thought of a new solution, not involving my leaky EGR valve but a reed valve, just like in the inlet of a 2 stroke. Then it's easy to defeat the ECU, the throttle valve can maintain it's original disc, all the controls can be original but instead of inhaling exhaust gasses it will be inhaling fresh air so it will be just as good as now, without the throttle disc, only a bit more complicated
Long story but i hope it's clear, other wise just ask and i will try to make it even clearer!