I need the expertise of the FI guys for my problem.

Its been over a month so far.... My 350 has been in 4 different shops, 2 of them were Nissan dealers. Seriously, why are all mechanics in socal incompetent? The first Nissan dealership couldnt find out what was wrong and said, we cant even look at this thing, its got some kind of intake and weird lines all over the place (oil catch can) ****ing idiots.

Dealership 2 looks at my codes...
1) Multiple engine misfire
2) p1148 closed loop bank 1
3) o2 heater core

The guy probably didnt know what closed loop was, so he said he could not test my vehicle becuase I had no front plate, LOL, so I got charged 95 bux to have my codes cleared, and I was told the car was perfectly fine.

Now I still have my wideband afr connected, and get this:

Before I brought the car in, my idle and cruising afr was at 18 - 20.
After dealership 2 clears the codes, my idle and cruising afr is 14.7, BUT
when I floor it, the afr jumps to 16-18 and the car sounds like ****. I do this a few times for a matter of a second or less, and the check engine light never comes on...wtf?
When I accelerate, the car hardly moves, it stutters and feels like it has 5 hp.

You would think the answer would be obvious with the situation and the codes... 02 sensor
But dealership 2 and mechanic 3 say all 4 o2 sensors are working fine. I feel like my only answer is to just dump the car off a cliff. Nobody can fix the ****ing car, its unbelievable.

Ive spent nearly $1,000 in towing and diagnoses so far. I dont know what to do.