Hi Daniel, that rear spoiler looks original with the parts# sticker (Needs some TLC). What about the rubber lip. Still in good shape? This was an E9 extra, could be ordered on a new delivery car or later as an add on and standard on the last lot of CSL's.
The front spoiler could be original too (I'm guessing based on the rear spoiler being original). If that's infact original and in good shape, it's rarer to come across than the rear spoiler. Again an E9 extra and standard on the last 167 CSL's.
The rear seats if original CSL, then that's cool! Don't recover them to match your front seats. Recover your front seats to match the rear. That would be a cool alternative.
Last but not least, the map reading lamp! If it's original, that's a CSL special and very rare to find specially with the fixture.
If all this just happened to come along with your 2800 (for no extra price), then you have plenty of (extra) reasons to smile.
Welcome to the magnificent E9 world.