The K&N filter issue has been covered many times, and in depth.

My 300SD... Aaron says its "destoyed" (chrome wheels)
http://www.peachparts.com/shopforum/showthread.php?p=840084#post840084

K&N Filter Efficiency Tests
http://www.peachparts.com/shopforum/showthread.php?t=114456&highlight=K%26N

K&N for the OM603
http://www.peachparts.com/shopforum/showthread.php?p=721322#post721322

K+N Filters - for a Diesel ??
http://www.peachparts.com/shopforum/showthread.php?p=710523#post710523

Air Intake Mod....
http://www.peachparts.com/shopforum/showthread.php?p=984631&posted=1#post984631

__________________
ASE Master Mechanic

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D

https://www.boldegoist.com/