What is the primary size? I don't want to take from this thread so an explanation. The 75mm posted from a Gen6 made me start running more simulations on exhaust primary and collector sizes. What I found is the primary size a little larger than 41mm and the collector size larger add a little horsepower. I suppose the balance connections might allow the primaries to perform as larger pipes. So I started looking, 60 and 65mm silencers make more power as well. I think the 75mm is planned and actually done to add power.