The car I drive the most when there isn't 2m of snow is the W123. I think I change the air cleaner mounts every two years or less, its annoying. When you change one you might as well change all three since you're in there, the front one is the only really annoying one because a socket doesn't fit well in there. I have seen this set up, it connects the cold air slot in the front to the turbo with a canister type box and a cone inside, no idea why this guy still has the EGR on it, I capped mine off with a plate. The original is over sized anyway, it will also make more room and better air flow around the engine in the hotter months. Japan is quite hot sometimes, I considered a summer bonnet to swap out with a slit along the rear of the bonnet facing back to let more air out of the bay. With the A/C going on a hot humid day I have had the temp climb a bit. The 1985 California W123s had a box up near the front and not mounted to the engine, if I could find one I might try that but its more complicated, this one in the picture hurts nothing and it can be changed back. This has been the only annoying thing about the car.

Time to get rid of the Merc air box