There is no way, I repeat no way, that the 997C4S can lap the Nurburgring faster than its RWD variant. Walter Rohrl did an official 7:59 with the 997C2S with Sport Chasis, so either he could do it faster (unlikely since that is already an incredibla time) or the 7:56 lap time for the AWD version is BS, the latter most likely since the AWD version shares same engine, suspensions, brakes, tire compounds, etc. except that it has viscous-coupling AWD which is always penalty in track lap times. Just to give an example, the 996C4 (not 996C4S) was 6 seconds slower than the 996C2 (same engine, suepsnion, tires, etc).
