[W126 Coupe] Air injection/EGR system questions

[Josh]

Would someone here be able to point me in the right direction to find
some info about these systems, on an early 80's 500 engine?

The reason I ask is that I am midway through refreshing an engine to put
in my 500SEC ('82 euro model) that appears to have a bunch of extra air
injection parts fitted to it at some point, likely when it was imported.

The engine that I am working over to replace the broken one with has
decidedly different parts fitted to the intake, and a lack of air
injection and EGR plumbing, other than the mostly plugged egr passages
under the intake.

What I am trying to figure out is what is actually required for this
car, what was stock on the car, and what I should just leave alone.

The only place I have seen the plumbing like I have on my replacement
engine was when I found a parts vendor that had some listings for euro
450 engines, which had some of the same fittings for vacuum and idle air
regulation.  When I look for parts listings on MercedesShop or the other
illustrated parts sources, many of them have no euro parts, or have
confusion and multiple prices for apparently identical parts, with the
higher price being "for euro cars" with no reason given. (this being the
tubular idle air valve in particular, which I have on the broken
engine.)


Well, if anyone can point me in the right direction to do more research,
or happens to have a stash of knowledge that they wouldn't mind sharing,
I would much appreciate it.

Thanks all,
-Josh