Here in AZ they can tell by the Vin# if the truck came factory equiped with a cat and if it is not there they will fail you. So pound it out and cut the ends so your 4" pipe fits through it and weld it in place. Now when they do the visual inspection it will be there and you dont have to take it on and off every year for inspection. When I took my truck in for the last emission test the P.P.M. test alowed 40 and my truck tested with 0 so I am not worried about eleminating the cat.