I just got one, I'm drannik, so I should get double the attack, but it still says 40 cloak, 20 attack.
Other modules changed name and stuff when installing them, this one didnt, is that normal?

The Modulated Xecti Weapons don't actually state the attack and cloak they provide, they just state what they can provide, its a simple graphics error that could be fixed.

Have you actually checked your attack to see if it has increased by 20 attack.

It does double attack it just doesn't show it on the graphics but it counts in your total attack. Just uninstall one and do the maths when you're not buffed.