Did not help at all...
the MAF sensor was quite ok.
Yet there is still "Lean fuel mixture on 1st bank" report
I had catalyst checked, there is nothing wrong with the fumes, they match all the regulations so the catalyst works just FINE.
I had all the spark plugs changed into new ones. Engine oil is new, changed 5W20 freshly as recomended.
There is "service engine soon" light on my dashboard and it doesn't want to go away. Why? Has this darn light nothing else to do, rather than annoy me? I don't know- go fishing, spend the time with family or friends? Nooo - it does remain on my dashboard, like a haunting ghost – saying “ service engine sooooon! Booooo!” maybe I should call the exorcist?
Ok, seriously guys, what should I look at to get rid of that orange light?

Why the bank 1 has lean fuel mixture, I use the best fuel I can buy, I never fill the gas tank with cheap fuel. Can that be the oxygen sensor issue? I had three sensors changed already, it helped a bit, but after a while the problem returned. Maybe the 4th one should be changed as well?
Do U think will that help?