Hi all - please forgive my naivety in all things wrx mods! New to the game and still learning.

I own a MY13 WRX, completely stock to the bone.

Putting in an aftermarket catted downpipe but reading conflicting messages about whether the car needs a tune after? Is it a must or just a nice to have to bring out performance bit more?

If it’s a must I’m assuming I’ll need a tuner that does stock ecu too?