Does the AI select the Z07/PDE packages? When I try and select the Z07 or PDE I get no opponents available.
Car can be bump started from 1 MPH or higher - just roll in neutral until 1 MPH, mash gas, dump clutch. Actually, you can just dump it into 1st from neutral at 0 MPH with the engine running and it will go.
...it also does nearly 90 MPH in reverse! (just throwing that out there because it's awesome)
Even more "important" now : please put a helmet on the driver as the default option. It looks silly without one while the NSX driver has one. You gave us the option, it should be default on IMO.
Along the same lines, would be cool to have the Z06 default to the older Z06 appearance, seeing how it looks quite similar to the ZR1 with the default upgrades. Would by handy for races with both Z06 and ZR1.

(Plus it looks cooler)
HUD looks waaaay better than the rF1 version, it's actually useful now! However, the hold over km/h tag by the speed is still there. Kind of weird when the dashboard speedo is in MPH. Now it is wrong for everyone, at least if it said MPH it would be right for MPH drivers.
Dashboards also seem goofed, sometimes it looks like you see the Z06/ZR1/60th logos all at once, GS has the Z06 dash?
Besides those few very minor points, absolutely fantastic. As with the rF1 version, the Z07 is the best of the bunch IMO, and gives the '91 NSX a good run for it's money for the best rF2 car. Drives quite similar to the rF1, little snappier and twitchier, but similar none the less. Fun car for circuit driving, but the Z06 is more fun for shenanigans. As said above, fantastic balance of power and handling makes them a blast to drive. ZR1 seems like it was an insurance problem waiting to happen without the upgraded tires, GS is friendliest of the bunch. Coupe feels like it should be driven by a old man like an old man - dee, I wonder why?
The reverb in rF2 seems to help this car sound better, but it's still underwhelming in that regard (though in fairness, I haven't heard a single high displacement V8 in a sim that actually sounds great, the dynamics have to be very difficult to reproduce!). No supercharger sounds for the ZR1, as was with the mod.

Shame in general, these cars sound great in the real world.