The GTS effectively has the same engine as the S model. It was more of a cosmetic upgrade to the car rather than a full blown performance step up. It will most likely have a sports exhaust fitted.
Here is a 718 Boxster S which I'm pretty certain has the PSE sports exhaust option fitted. The turbo 4 cylinder has much more of a bassy sound and doesn't have the high pitched scream as you pile on the revs that the flat 6 N/A engine has.
https://www.youtube.com/watch?v=OQqO8DUQTlg
What the ........ does it sound like without a sports exhaust?
Seriously, I'm sure they're fantastic machines but that sounds pretty poor for a high performance sports car, and I'm being very, very kind. The 6 cylinder was 'ok' although I wouldn't necessarily describe it as a high pitched scream.
Maybe I've been spoiled by listening to Ferraris with sports exhausts for too long.
As I say, sure they're great machines though :thumbsup: