why do you want to remove your cat for? if its for more horse power please don't because even with a nice header and exhaust its been proven that it'll net you 1-2 horse power, which is not enough to really make a difference except to pollute this beautiful planet we live on *hugs a tree*
but, if you are turbo'd and want to remove it for better exhaust flow then you can run a test pipe or high flow cat and then have your tuner turn your o2 sensors off so your ecu will not even search for it *cuts tree down*