this is just a question but my car has twin 400 cell cats, but how much better would my exhaust flow with say twin 200 or 100 cell cats, as i dont want to de-cat my car, and how would changing my cats affect my exhaust emissions?
Emisssions in theory should go up slightly, but cars can pass the test without having a cat in place so as long the engine is in good condition then it shouldn't be a problem with ether.
decatting isnt really an option now as a visual check is supposed to be done. id probably go with the 200s
A lot also depends on the size, some sports cats are larger than conventional ones and the flow rates are comparable to a decat. Emissions shouldn't be an issue with either but I'm not sure it's worth wasting much extra money on a 100cell over the 200.