I am considering removing the cat since I no longer have to go thru inspection due to its age. Is there any performance advantage to doing it?
I don't think you'll gain anything. But, as old as it is, I doubt it's working at all anymore. We went through MANY in our 350,000 mile 318 Ramcharger. Always failing smog for NOx, every year or two, always the converter. Near the end we discovered those muffler shop cheapies were universal fit and crap. Finally got one from Walker, specific fit for the truck, lasted until we sold it in 2016.
