Your cats won't be damaged or anything but a tune will maximize your gains from your mods plus the other benefits like fixing the stock throttle map, multiple fuel maps, data logging launch control..etc.. and the tuner can turn off your cel light as a bouns.
However, if your sole reason for tunning is getting rid of your cel, then you can get a j extension/defouler for your o2 sensors and it will take care of your cel without the need for a tune.
Im running them on my car
