So I just recived my new exhaust manifold which I will be fitting tomorrow.

It seems to have something I have not noticed before on it though.

Now what I have does not include this plug. Is it necessary? What is it for?

Thanks for the help! Image below.

 

It seem it's a universal O2 sensor you have another one toward the end

 

it's for the o2 sensor. If your car has the sensor on the manifold by the engine, it goes in that hole. If its down the manifold in front of the cat, then you use that hole. Pretty simple. I believe 96-00 have them in front of the cat, and the earlier 92-95's have them up by the engine.

 

MY Si has it onthe cat and another one in front of it.

 

Perfect thank you!

I see why now why the hole nearer the engine doesen't have a plug. I have a plug in the hole further down, so that plus will be in either one.

Thanks for your help - problem solved!