I've brought my car to two different shops and my dealership for maintenance when I didn't have my cats on, they didn't even mention the matter. The reason why I decided to throw on cats was because I was pulled over for an "altered exhaust system" and I had to have my car inspected, turns out the cop didn't even look under my car what so ever. I personally like my set up now with the cats on, it cleaned up some rasp and I don't even feel the 5 hp loss or however many it is.
Also, if you need a off road shorty x-pipe I have one for sale
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