Q: Is the air coming in from the bottom of the engine, then going through the turbo's and to the valves or is it coming from the top of the engine, going to the turbo's and going back up to the engine? http://www.onlinemodelcars.com/sites/pwaters/_files/Image/bugatti-veyron-w16-engine-776255.jpg
A: Your first thought was right. The clue is in the color of the airflow in this diagram. The cool (blue) air is entering the turbos at the bottom of the engine. It is then passing up to the inlet manifold at the top of the engine. The narrow pipes are bringing hot (red) exhaust gas, under pressure from the engine to spin those turbos before leaving through the large size pipes at the left of the diagram. The diagram would have been clearer with a few arrows to indicate what was happening! (Bet it sounds good though!!) Hope that helps.