Get yourself a compression tester and check the compression both dry and wet, this should tell you what nick the piston rings are in, and can then potentially rule them out if the result is good.

Also my RS turbos bonnet only had the one vent, on the passenger side. I presumed this was to prevent water dripping onto the air filter, amal valve and battery
So i wouldn't say this was fitted to hide any problems around the DV area, probably just a coincidence.