[Vpmedia]

I've found two submods which lowered my fps.

1. the increased visibility distance of the smokes
2. the longer livetime of the flak smoke

#1 is in the file:
C:\Program Files\Ubisoft\IL-2 Sturmovik 1946\MODS\DAMAGEMOD\Effects\Materials\WhiteSmoke.mat

you need to set
from
VisibleDistanceFar 10000.0 // Float 0.0 - near, 1.0 - far
to
VisibleDistanceFar 3000.0 // Float 0.0 - near, 1.0 - far

#2 is in two files:

C:\Program Files\Ubisoft\IL-2 Sturmovik 1946\MODS\DAMAGEMOD\Effects\Explodes\Air\Zenitka\USSR_25mm\SmokeBoiling.eff
set 'LiveTime 5.0' (this is the default value, cant remember exact moded value, was around ~3000)

C:\Program Files\Ubisoft\IL-2 Sturmovik 1946\MODS\DAMAGEMOD\Effects\Explodes\Air\Zenitka\USSR_85mm\SmokeBoiling.eff
set 'LiveTime 10.0' (default value, I use 100)

If you install 4.09b1m it will increase your view distance by aprox. 1 km without fps loss.