Scotty please please help me. My k s o is in perfect condition other than what's wrong with it LOL.  I have to laugh to keep from crying.

It originally threw codes.0303 and 0304 and ship and sputtered like it was just gonna fall apart.  I'm loose by plugs.All new Ignition coils change the oil.New air filter PC v valve clean the intake.And fuel injector system by dumb by steam cleaning it I think.  Put in a different transmission that only had sixty thousand miles on i. Still misgifing to this day.  But now it has code 0304 and 0256 small vacuum leak.  

All quality parts were installed.I am now driving it to see if the check engine light will come back on because it's init.Corals were switched between number four and number one.  Still waiting.  105,300 miles. All minyenancesnce done on time

  Had car since 2018.  Never anything wrong except alternator replaced last year.  Drives perfectly except for occasional bucking due to mixgire.  When the transmission was replaced it still did the same zach thing bucking.  It bucks worse when I accelerate but not always.  I desperately need to get it fixed so that I can sell the car and get another one.  I would never sell it to anybody knowing that there is a problem.  I'm Afraid to take it to Kia.Because I know they're gonna screw me. 

so please help me.  Edith (Bloopie)