Hi I was just checking over my intake system and found that the front air intake box (attached to front grill) has no back part so it's not a sealed box. Is this normal or is a part missin? If so where can I pick up a new one. Cheers for any help. Car is 2011 Audi A3 tdi if that helps 

i noticed this too. i have no idea what the logic is behind this, but mine is exactly the same.

i recently had to replace my air intake temperature sender because it was contaminated. At this exact time i had an oil leak somewhere and it lead to the oil being vapourised inside the engine bay. Because the back of the air box inlet is open, i believe the vapour was sucked into the air intake and blocked the MAF sensor.