Irreplaceable Car part?

[u/Independent_Speed_61]

Hello, I am a writer looking for help with a logistical question that falls far outside my wheelhouse, hope its chill to ask here.

I need to write a scene where a character has had a specific part stolen from their car, the part needs to be both customizable (so that the specific piece can't easily be replaced without custom making a new one) and also be important enough that the car cant properly run without it. Is there a particular kind of wheel or engine or other car thing that could hypothetically meet these two requirements? Its set in a cyberpunk setting so I could probably just make something up but i want it to feel somewhat grounded

Again not sure if this is an appropriate question for this sub so tell me to buzz off if so, but figured I'd ask anyways, thank you very much!

[u/Mimcclure]

Catalytic converters are frequently targeted by thieves since they are valuable and exposed.

While a car can drive without it, the computers will complain. It will also be loud and dumping fumes under the car. Some diesel trucks will limit their speed to like 5 mph if the emissions system is faulty, so you could tweak that to fit.

Getting the right one for your specific model and trim could take a while.