I agree that the B-17G does get to run at a slightly higher power setting than maximum continuous power, however it is not running on WEP continuously. Matter of fact it's not even capable of military power. In my off-line testing I was only able to get 46.5 manifold pressure not 47.5.
Another aspect that's over looked is that the engine model will not give proper continuous power at 20,000 feet. At 20K you should be able to pull 2300 RPM and 41.5 MAP (up to 35,200 feet) in game you can only get 38.5 MAP at 2300 RPM. So in essence the engine model is all ready limiting the speed at altitude.
Looking at Frame 1 and 2 the Luftwaffe have shot down a higher percentage of bombers than was ever achieved in any heavy bomber attack on Germany. If the 8th AF had this high of a loss rate the daylight bombing campaign would have been halted.