I don't know how many other models of MBZ this applies to. But I just noticed when I pulled the snorkel tube away from the airbox (Air filter compartment) that the intake hole was much smaller than the tube or the outside housing. There was a large plastic restricter inside. I was able to take craftsman tool that is similar to a leatherman, and with the thick folding knife blade pry out the restricter where the restrictor and housing meet.
I took it for a spin on the freeway, it seems to be a must more enjoyable drive. This was done on a 1987 190D.
You might as well try it. It will snap back in place if it doesn't work for you.
Cmotif <><