Hey! Love your mod :)
If you place two modules: module (G) (-75% pollution ) and module (B) (+50% pollution) into a vanilla Electric Mining drill the result is:
Pollution 11.25/m (-25%) form the base 10/m (0%). That is not a a 25% drop, but a 25% increase.

Hello,
that sounds like a bug in the base game. I was able to reproduce the bug and will report it to the factorio devs. :)

thanks :) hope it will be fixed and more fun to play with zero pollution runs

I did some more tests, actually I can't make any sense from the numbers I get on pollution from any modules that alters it (the % and the value do not correspond to each other), even for Vanilla modules. So it's not a module combination thing. Might help with zeroing in on the bug.

I'm very sorry, I was badly informed. Please close the bug ticket for the dev team, that you opened.
at https://wiki.factorio.com/Pollution
"Final pollution value is (pollution multiplier * energy usage multiplier * base pollution)."
so module (B)+ module (G) = ([+50-75]/100) * ([+250-200]/100) *10 = 11.25
All is as intended.