Forget BHP - history is littered with high torque/low rpm cars being made available to the public with the same results pretty much every time.
Whilst I’ve not driven the P6 - there will be additional factors like - throttle butterfly speed, with throttle by wire, throttle butterfly speed in many cases is not matching the peddle (ie. closing slower in comfort mode). Gearbox programming for auto’s, the propensity to drop a cog or rev-hang in gear.... even with throttle peddle off I’ve been in other cars where they will actually speed up not slow down.
That’s before you get to the mechanical grip of tyres and suspension set-up.
As for Aero’s....... having tracked my S1.... it’s considerably better on a track pushed hard than on the road. What let’s it down is the Engine and Gearbox. The engine runs out of puff and does not have enough revs to play with and the gearbox is designed for a heavy saloon.