Preventing apps from detecting other apps
After extensive searching found an Xposed module for it! 
xPrivacy! 

EDIT:

xPrivacy (http://repo.xposed.info/module/biz.bokhorst.xprivacy) is an Xposed module that allows you to control what data apps can access (it's more powerful than app-ops or ReceiverStop but more complex).  

so what i did:
after installing xPrivacy


Scrolled in the app list to find the blocking app
Pressed on the picture
Scrolled in the restrictions list to "system"
pressed on the arrow on the left to expand
disabled relevant restrictions (serv_getInstalledApps,serv_getPackageInfo etc..)
Had Fun :)


Hope this helps
will be more than happy to add more info if needed :)