Additional Proving Ground Engineer
Upgrade the Proving Ground facility and add an additional Engineer to further increase the manufacturing speed.

The mod will stick to your savegame, and as such, back your saves up prior to enabling this (or any) mod. 
You can find your saves at "..\Documents\My  Games\XCOM2\XComGame\SaveData". 
As a general rule, try to do it for any games that you use mods with. 

Installation: Extract the .7z file to ...\XCOM 2\XComGame\Mods folder