Welcome, love the car, looks fab in the LG.
Your correct starting with the Haldex, make sure the filter is removed and cleaned with photo's as well.
Check the front prets for buckles, they are prone on our roads.
Get the Audi jacking points fitted so it wont get damaged lifting.
Extended underbody tray to protect the sump - a must
Look at the CS front discs and pads, they wont rust out anywhere near as fast.
Tyre wise put the PS4S on, make such a difference
Enjoy and stop looking at the MPG, its the wrong car for that!