I think we got there.
If there's no EGR there at all, you will get an error, since the ECU tries to communicate with it and gets upset when it doesn't get a reply.
If you have no EGR there, you have to blank/seal off the pipes to and from it, otherwise the exhaust gas that normally passes through the EGR ends up in the engine bay.
If your EGR is new/clean and moving properly and fitted in place (technically it just has to be plugged in), you won't get an error.
If your EGR is in place/plugged in and doesn't work properly (stiff/seized or knackered) then you'll get an error because once the ECU has contacted it, it also checks to make sure it's working properly. Your old one wasn't (I guess), so this is what gave you your original error message.
If your EGR is working and you fit blanking plates to isolate it from the exhaust gas, then it won't give an error, since (as above) the ECU just checks it is there and it receives the correct signals from it.
If you're not now entirely fed up with EGRs

you can fit blanking plates around your new EGR so that it is closed off and works, but isolated from the exhaust gas. But.. since it's brand new clean, if you don't do lots of short journies (and even if you do) it's going to take a very long time for it to get clogged up again, so there's no rush.
Ralf S.