Speaking to the owner of Abarth racing the other week and he said the 500's come with anti-lag straight from the factory. He asked me if I noticed the exhaust pitch changing when you push the clutch down at idle, indeed I had but didn't think anything of it. He told me that noise is the anti-lag turning on, apparently one of his customers has re-wired the switch (which is under the clutch) to his dashboard so he can have it on all the time whilst racing.

After some googling I can't find anywhere that confirms this, anti-lag almost seems pointless with such a tiny turbo?

Intersting. I had assumed the change in note is cosmetic to get rumble whilst changing gear...

Anti lag is hard on the turbos.