It is two sensors per downpipe.So noob question, you still run at least a pair of O2 sensors, one O2 sensor per downpipe? This is so you can get the AFR for tuning purposes correct? Or did you plug them all, which doesn't make sense to me, but then again thats why I am asking because I would like to run DPs in the future on my FFS.
I just plugged one, I am going to try and extract the seized one using a torch eventually and re-install it (can easily do this one from above the engine). You will need at least one so the ECU can read and automatically adjust lean/rich conditions.