Mobbsy

Im looking at putting a set of headers onto my 99 is200 that go into a 2.5 inch straight pipe with a sports muffler on the end and a high flow cat converter, I'm not sure will i need a tune after i do this exhaust or can i get the exhaust done and drive it for a few months then put a tune on the car? the headers do not have cat converters but still have the same factory, O2? sensors and the same with the new custom pipe.