I feel like an idiot asking this but here goes....

I'm poking around on fcp groton looking for oxygen sensors because I believe I have narrowed my problem down to those. I find 2 of them, one before the cat and one after.

So I put the car up in the air and I start from the back.

Muffler.... ok good ..... a resonator... ok good ..... the cat (or so I thought) and then oxygen sensor #1, flexpipe, oxygen sensor # 2.

What the hell? Are there 2 resonators besides the muffler, and the cat is somehow hidden up in that tiny little flexpipe?

On my E46 the cats are in the manifold, I did not expect to find something equally whacked out on this car.....

 

It's after the flex pipe, right before the first flange.

 

Hm... It looked like there was one oxygen sensor on either side of the flex pipe. Maybe I need to look again...