There is one that I know of, can't remember where I read it, they had the base, S, and GTS, the review was that the base is fine on public road, it lacks power on the track. The S and GTS felt the best on the track and can't really tell between the S and GTS in terms of hp. The writer said, I will assume the GTS is faster b/c it has a few more hp. The GTS sounds the best. I remember a picture of all three on the track, appears to be going downhill, almost looks like Laguna Seca. I have many car mag subscriptions so can't recall.Has anybody seen a head to head compo between a 981 GTS and a 981 S yet? I would be very interested to see something where the cars are similarly spec'd to see how much difference there is. I suspect this may be something not officially endorsed by Porsche...