I have a turbo XS catless Downpipe and want to know what side I should get the bung welded on for the wideband? And right after the flex pipe correct?

 

...you have a factory wideband...you don't need one.

 

^^It's never a bad idea to have an in-car wide band seperate from the built in stock one to monitor what's going on with the engine, especially if you're tuned.

OP, right after the flex joint is fine.

 

He can also remove the emissions o2 sensor for cat detection...

 

Well I have one just sitting around I was going to put in my truck but with it being for sale I figured I would just throw it in the car while i have the downpipe out since I won a dual gauge bezel. I was just wondering what side of the Downpipe had room so I don't weld the bung and not have room for the O2 sensor