Hi there.
Over the past few days my 1983 300D has been sluggish while going uphill.
It would occasionally "flatten out" (no acceleration) as I was driving it.

Tonight I drove the car about 10 miles...
As I left my home it did the same thing. By the end of my trip (on my way home) the car would barely even move. I would have it floored and it would barely be at an idle.
It would do a little better (but not much) in park and neutral. By a "little better" I mean that it would chug for 4-5 seconds then rev up. Other times while parked I would give it gas and it would just chug.
When I let it sit at idle it will idle fine at times...then at other times it will just die.

My inline (pre) filter is very black but I am able to blow air though it (I do not know if that matters or not). I have yet to open the secondary (main filter) as I do not think there is a way to visually check it.

Both of the filters were changed about a year and a half ago.
There are only about 10,000 miles on them.
Whether they are the problem or not I will be replacing them tomorrow.

I use petroleum diesel and I do not suspect algae to be the problem.

I guess my question is:
If it is indeed the filter(s)... Is it normal for the problem to develop so quickly (over 5-6 days time)?

Does anyone believe that it is the filter(s)?

Thanks you for your time and help.