The F1 GTRs and CLK-LMs are on stock setups while the 911 GT1s are fully upgraded with max racing parts, the Gr.3 F1 GTR is grouped with GT1 because in the 1997 FIA GT Championship BBA Competition used a Shorttail F1 GTR even though it was very much outclassed by the current GT1 cars but was too fast for GT2, it was only somewhat matched by the few 1996 spec 911 GT1s being used as those were also outgunned by most of the GT1 cars except the Elise GT1s as those weren't really all that fast.
The GT2 Cars are all tuned to 450 HP with max racing parts otherwise.
I have also since removed the 2 Alfa Romeos as they are far too slow even with the High RPM Turbos they are barely faster than the GT2 cars, instead I replaced one with a RUF CTR3 taking place of one of the 1996 911 GT1s tuned to match the F1 GTR Shorttails performance with 536HP. The second one is being replaced by the Alpine A220 taking place of the Callaway GT2 because in a black livery the front of the car strongly resembles the GT2, and even though there was only 1 Callaway GT2 used in FIA I am keeping the C4 Corvette for variety.
The GT2 cars are all competitive with eachother while the GT1 cars vary depending on track, on tracks like Le Mans the 911 GT1s are extremely matched with the GR.2 GT1 cars while on other tracks they lag behind, mainly due to the 911 GT1 not having any weight reduction available as I feel if it could be made lighter it would be very competitive with the CLK-LM and F1 GTR on twisty tracks.