haha, silverS2 it was supposed to be, your right it delays the opening so the exhaust valve , but i dont think its shifting power downwards, more like it increasing the filling of the cylinders and there efficiency at higher rpm ( more than 3000rpm) until they reach a restriction in the system, the drop at the top end your talking about is probably the turbo and exhaust manifold and system that start building backpressure which then becomes a traffic jam and decreasing or flatlining the top end, thats with a stock/small turbo, with my dyno graph you can see there is no loss or flatlining upto, its just keep climbing cause theres no restrictions.
advancing the cam would make the combustion more efficient by decreasing the overlap,