Many years ago I read that a certain German tank commander somehow improved the power output and mileage of tanks. Specifically in a hot climate, as he was stationed in Africa. The modification does not add any components onto the engine, rather if I remember, it involves boring something into the intake manifold area. After exhaustive searches I cannot for the life of me find what that was, but I do believe it was mentioned somewhere on Wikipedia. This modification became popular with many Diesel or petrol engines on both sides of the war and I think up until injection was common place. I believe it may involve a supercharger/compressor but please don’t quote me.
What was this rather simple, field modification that improved engine performance?
Since it looks like no answer is forthcoming, consider asking over at r/WarCollege. There a few folks there that would definitely be able to answer.
I imagine, however, you are referring to the intake valves and dust filters used originally in cars. See this paper: Desert Warfare: German Experiences in WWII. I also think one of the Osprey books addressed this modification. For the life of me, though, I can’t recall which, and during a library downsizing I unfortunately gave away mine. There was another modification made which I cannot recall, and it may be that which you’re remembering. I recommend seeing if you your local library or college library has the Osprey books on Pz III or Afrikacorps in stock.
(To the mods: I recognize that this isn’t a detailed post and probably does not meet the sub’s requirements. I cannot speak in detail to Afrikacorps’ operations—only tanks’ performance on the Eastern Front. However, I figured it better to provide the OP with a starting point until a better answer arrives given the lack of interest so far. I held off from posting for several days to allow time for a better answer to emerge before posting this. I understand if it needs to be deleted.)