Firstfives.org

I noticed that this 1980 528i has Exhaust Gas recirculation system , My spare parts car - a 1978 528i also has it.

whereas my 1977 528i and 1981 528i don't.
These are all RHD Australia delivered cars

So I'm looking up the WWW to find out about more info on this system, and indeed do I still need to have them.

found
https://www.cambustion.com/products/egr
which has a reasonable explanation

Scotty Kilmer has a couple of videos on them
https://youtu.be/XgfT3kuY8lc
https://youtu.be/8zLgmL7iBqI

Firstfives FAQ has a write up by Robert Bondi - in particular how to remove the EGR system
https://www.firstfives.org/faq/ljet/lambda530i.html

I suppose my main query is why there is such in difference in the application for the different years - does the 1981 car have a different system altogether.

1981 2.8i


1980 2.8i with EGR

and a sticker on the hood

Different countries took different approaches to emissions, and there were also changes as time went on. Some mandated certain equipment, which might or might not include EGR, and others just listed what standard it had to meet and left it to the manufacturer. Any chance the '81 has an O2 sensor and cat? Here in the US when that came to us on the also new to us 528i, seemingly everything else was dropped emissions wise. It was effective enough nothing else was required to meet US standards at the time.