NHTSA Complaint #11419765 — 2013 KIA SOUL

My car, KIA SOUL 2013, had problems such as 1.car burned oil a gallon every 500-1000 miles 2.car not accelerating properly 3.check engine light PO420 and there was a recall about catalytic converter so I went to KIA DEALER (DTLA). I expected them to replace the catalytic converter but they just upgraded ECU. A couple months later, my car died in the middle of mountain road. According to a mechanic, one of engine’s pistons not working and suggested me to replace an engine. I did because I need a car for working. My car now still show code PO420. I am afraid that my car will die again from malfunction catalytic converter