I'm do for smog and my CRX doesn't have a cat. All it has is 2 1/4" or 2 1/2" (not sure what size it is) piping strait from the manifold to the aftermarket muffler. I know I'm going to need a cat, but does the pipng size matter in order to pass smog? Also, should i get a stock cat or a universal one? I'd rather not get a high flow cat as the car is just for commuting. How much am I looking at to get this done?

 

i think you might want to get a universal cat and take it to a good muffler shop. i doubt that your piping would matter since they have adapters for the piping. to weld them in will run you probably around $40 at the most. with the cat, well just shop around. good luck.