83 240D suddenly gets power back. Why?

[Carrameow]

My 83 240D's performance progressively deteriorated over the summer. At first I didn't notice it; I thought the Air Conditioning was bogging performance down. The acceleration got worse and worse. Since a 240D is not exactly a powerful stunner it was hard to notice at first until my 4 passenger Carpool almost got smeared by a Truck.I thought it was a Linkage, Fuel or even blocked exhaust problem. i got ready to break it down next weekend.
Suddenly today as I was driving I suddenly felt a Power Surge and then its old performance returned. At least now I can cross a bridge or climb a steep hill in 4 th Gear again. I can again use the car safely in my Carpool now.
What happened? Did I suddenly "unblock" a fuel line? The return in performance is stunning! I'm very curious so I know where to troubleshoot the next time.

[Stan Pittman]

Just a guess and it would be a first sounds like one of the fuel filters unclogged.

[be459]

broken air filter element or air filter housing?

Good luck

David