The hole in the air filter is for fuel mixture adjustment & dirt can't get into engine from there.
The plastic line goes to the fuel pressure regulator, it comes in a one(1) meter length. Part number 000-158-93-35.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)