Mandoble, I understand that.
But in the VK107 a change was made after WWII. I can't remember if the new designation was VK107A or VK107B
If I remember right, it was the addition of water injection, but I don't have the aircraft engine book that I read that information in. I was considering buying the book while reading it in the US National Air & Space Musueum bookstore, but in the end, I didn't due to cost since it was about $80 US and I already have several books on aircraft engines.
I'll check my other books to see if they list that engine change. But I do know for a fact that the engine in the Yak-9U during WWII was different from the engines in the Yak-9U's made after the war.