Saxy - do the maths, these are all same day tests by respectable sources. Cup 2 1.2s/minute faster than Cup+.
Trofeo 0.4s/minute faster than Cup +. Sport Auto test.
So Cup 2 is ~0.8s/minute faster than non-R Trofeo and the non-R Trofeo is still faster than Corsa Systems.
Now at Portimao the Trofeo R on the P1 was 0.9s/minute faster than the Corsa Systems.
So in summary:
Cup 2 > 0.8s/min > Trofeo > Corsa System
Trofeo R > 0.9s/min > Corsa System
Good luck find 1s between the Trofeo R and Cup 2 in there.
Now Harris ran 1:56 at portimao with the 918 first time out and 1:53.98 the second time, with the same tyres. Now if he'd used Trofeo Rs the second time and ran 1:53.98, the internet would have been full of idiots claiming it was proof that Trofeo Rs are 1s/minute faster than Cup 2s, which is exactly what they did after his different day tyre test.
Why did Chevrolet put Trofeo Rs on the Z28 and then have Cup 2s as the option tyre for Z06s?