I would think you would be fine unless your laws and regulations are like Commiefornias where you cant touch the cats period, but since you are just swapping out the cats with high flow ones you should be ok. To be sure you might ask some local shops or do some research on your states requirements for a better idea of what you can and cant get away with.
Should be ok you aren't removing the cats completely, I would ask some shops around your area since they will know what kind of laws and regulations you have much better than I will.
Hello sir, nice to have other car crowds on this forum!
One quick question if you don't mind.
How long did it take you to get certified as an Automotive Tech.?
I'm trying to get that done and then during next summer I might go to Tenn. to get my high performance certificate.