[Mangas]

I had the same problem -- but exactly vice versa: my almost all a/c engine sounds in 0.93 are so loud, that it's almost impossible to fly most of the fighters... But bombers, quite opposite, are almost inaudible...
So, I think these problems come from sound recorder settings of guys who developed this mod.

So, there are some different sound settings in game: "Effects sounds", "Overall sounds", "Internal sounds" (I heve Russian version so I may only guess the English names)... I recommend you to try to change them...
Besides, try to disable/enable "Hardware acceleration". My sounds became better after that method...

Good luck.

Mangas.