Just had a quick question I'm hoping some of you can answer. I'm planning on getting fast intentions high flow cats here soon and there is an option to get an extra O2 bung on drivers side, passenger side, or both.

From what I'm gathering it would pretty much only be used for either tuning or on a dyno run. In everyone's experience, especially people who have these HFC, is this needed? And if so is it just another section welded to the HFC that something like a reader or O2 shaped item goes into, and if so, when it's not in use is there a block off plate that should be put there?