what would happen to my car if i didnot replace the catalytic converter?
Depends on what you put in its place.What’s your plan?
Unless the catalytic converter is plugged, collapsed, or burned out, and cannot pass emissions, you don’t need to replace it. I never replaced the cat on my 1990 Toyota P/U with 325K miles on it. After the retaining wall stopped me from getting to half-a-million, I pulled the still-good engine, and the cat was still in great shape. The front of the grid was only slightly eroded, and you could still see daylight through it. Also, the truck passed emissions (driving simulator) 5 months prior.
If it ain’t broke, don’t fix it.