My brothers went, black VTS & white R5GTT.
All they said was the rolling road was bollox, not at all accurate. Came up with very wierd figures.
VTS got 134bhp & 161lb/ft (last RR 159bhp & 149lb/ft)
GTT got 120bhp & 160lb/ft (last RR 139bhp & 170lb/ft)
The last RR figures they got were from a local place that we know is accurate.
Both cars have had quite a lot of engine work done, and unfortunately I know they are quicker than my 145bhp Valver.