primary is normally on the manifold itself but i wouldnt run a primary at all just secondary and tie the primary up...and really just gonna half to find a place where the o2 will fit... needs to be sitting upright or anything past the 90 degree mark on the upside... never let the top of the o2 point down at all bc it will not last long at all

if you half to run primary you will half to put it about 1 1/2 to 2 ft past the outlet on the turbo so its measuring all the air and not just from one runner as it would be if you put it on the manifold