This is a if you could how would you build it question/discussion. If you wanted to build a header to run one O2 sensor per cylinder and had no restrictions on space how would you design it. What tube diameter, O2 location, How long should the tube be from the sensor to the collector to prevent backflow from generating bad O2 readings. Looking at building or having a turbo header built. This started with my brother wanting to turbo his legend car for autocross racing. It got me looking at changes on my planned build.