How to gut the cats....first remove the exhaust from the car...next you will need a grinder with a cut off wheel to cut a 4 inch by 4 inch square on the cats...save the pieces you will need to weld them back on....once you have the square cut out you will expose the guts in the cat...take a screwdriver or chisel with a hammer and break up the guts...make sure you get it all out...weld the squares that you cut out back on n bolt it back up...done