You mentioned that you haven't checked for exhaust leaks.
I had a P2A00 and my car was running sluggish and chugging gas, no misfires but just bad. I came on here to try and find a solution, everywhere I read it said that it was probably an intake leak, turned out that I had a crack on both catalytic converters. The crack was downstream the O2 sensor on the exhaust manifold and upstream the O2 sensor on the cat. I had aftermarket cats so I put the stock ones back on and it solved my problem.
I understand that you have stock cats and it is very difficult to damage them, but try and rule out an exhaust leak in that region.
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