fuzzysig

im out of ideas on what it could be

owned the car for almost a year and checked everything i know

1 black smoke on acceleration
2 car feels like it stick in high gear when accelerating. instead of downshifting it just stays in gear and takes forever to accelerate
3 somewhat sluggish on low rpm
4 bad city mpg(13mpg) but normal freeway mpg(30mpg)
5 no codes whatsoever for anything.
6 bad smell when car accelerates and especially when it doesnt downshift

i had flushed transmission with redline d4 it was recommended on acurazine
fresh oil and filter
valve adjustment
there are no oil leaks or oil burning besides a small rear main seal leak
balanced and rotated wheels with new tires
allignment done
spark plugs look new and ngk the correct plugs

i keep scanning it with autel shop scanner once a month but there are surprisingly zero codes for anything at all
it has 178000 miles original everything

so far i was suggested pretty much the usual suspects
wideband is bad or both
catalytic( one of 3 or all 3) are bad
transmission solenoids are bad. which wouldnt explain bad MPG or sluggisn low rpm only the shifting issues
no fn idea what is the problem
i run tests on pretty much every component separately and it passes so the shop scanner is not helping