The Nissan Path

Been having this issue with my A/F sensor reading lean shift on bank 1 and I have a good idea as to the problem but I was hoping for a little insight before I drop the hammer on the dealership for bad work bolting catalytic converters on my ride.
First let me tell ya what I've tested and replaced. I've replaced both A/F sensors, intake collector gaskets and spark plugs. I've tested for air leaks in intake manifold on bank 1 side and for exhaust leaks at manifold bank one side. I believe when the non Nissan dealership installed the cats they didn't properly fit them to the exhaust manifold and so that might be the problem. I have a pic of the joint but haven't figured out how to post it in this post. There is a noticeable gap, 3-4 mm, between the cat and the manifold on the bottom side of the joint.

I had the dealership that I originally bought it from take it back in and they then took it to a third party exhaust place.( the original place that put the universal cats on) They handed the vehicle back to me and said it was a few small exhaust leaks on the back side of the cat and repaired it as necessary. I also had them drive it 30 miles to check and see if the SES light would come on. When I grabbed the vehicle there was no light...... Until about 5 miles off the lot! Went directly to the nearest auto zone and had the SES light read. Same code.