I did replace the K&N today.

I also cleaned out the air box and it's drain tube.

It was full of sand and dirt that kept recirculating in the box.

The previous owner worked cattle in this car on muddy roads.

The transmission has mud caked on it.

There was grass, sticks and an inch of dirt/sand in the air box when I replaced the air filter and I noticed that under the plastic underbody aero work there is untold amounts of dried mud.

I plan on servicing the tranny and replacing diff fluid soon as well.

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1993 W124 300D
-297K on the clock as I type this.