The cat isn't needed for the operation of the vehicle. It's there to partially remove nitrogen oxides from the exhaust stream. If you remove it your car will function just fine, the exhaust will flow a little more freely and EGTs post-turbo will drop slightly. Your engine's power output may also rise a small amount (and it might not).
However, it is illegal to remove it. It's just as illegal to block the EGR too, although blocking the EGR has many more and greater benefits than removing the cat.