The length of the primary exhaust tubes effects the performance of an F1 engine. These are the parts connected directly to each cylinder. They must all be tyhe exact same length and this length is crucial to the performance. The length directly effects the resonance within the exhaust. The ideal situation is to have a negative pressure wave flowing when the exhaust valve opens. Thus helping to draw out spent gases from the cylinders. Also during valve overlap this helps to start the flow of fresh air/fuel mixture. Conversly, if there is a positive wave acting then it will hamper performance as it will act against the spent gases and try to push them back inside the engine. To prevent this happening engineers have to experiment with the length of primary tube. However, it all depends on the engine revs at the time. Sometimes it works for you sometimes it doesn't.
Hope this helps
