The FX was visually faster mid corner in slow corners thn the AMS car.. and those were much faster than anything else out there - including the Autometrics Porsche GT car.
The AMS Evo looks to dig out of corners better - which was always it's strong point when I was in it. The FX NSX is stupid fast as speed get higher, but does not look as fast as a GT1 trans am style car on top end.. it could be that it's nto entering the corners well, and so the driver is slowing down earlier - he certainly looked to be braking earlier than most, and earlier than GT1 SCCA cars. Talking to a driver on track with the FX car also seemed to confirm longer braking for many of the corners and slower entry into the higher speed corners.
Now.. none of that is backed up by any hard data.. but I have watched many many cars run around CMP.