I would not gut the cat. If you really don't want the cat there cut it off and replace it with straight pipe, thats what I did. If you gut it the exhaust has a large resevoir to expand in, and then the engine has to compress it back into the pipe which requires work (basically it completely disrupts the flow of the exhaust). If you think your cat is robbing you of high end power, replace it with a high flow cat, but gutting it is the on of the worst things you can do to your exhaust system.