I am using an IHI turbo on my d-series custom turbo setup and the O2 housing in the downpipe section is being used and I am using a STD manifold with an O2 housing and I am wondering which one to put my O2 sensor in and whichever one I dont use do I just plug it up? I know this may sound dumb but this is my first custom turbo setup and I want to use the IHI O2 housing downpipe section for my downpipe and am wondering about having to sections for a O2 sensor and which one should I use?

 

bump

 

you can use either/or, it won't make a difference really. The closer you put it to the head, the faster it will warm up, that's all. Plug the other hole or use it for an EGT gauge.