I think you are right. After researching more I guess it is detonation related, and from all the possibilities, this one fits better (I will also try higher octane fuel, but I do not think this could completely fix it).
Where should I start with lean mixture?
I am not a professional at all, car was given to me to go to college but I can tell maintenance has not been good. So I am trying to learn things and do it myself
. Of course, with a lot of research and patience in the process to not make anything explode.
Well, as for now, I can assure that fuel filter looks very old, probably injectors are dirty too. Btw, no check engine light at all.
I do not want to replace or buy something that won't help at all. I appreciate the support.