Oh the Z/28 is definitely the real deal, but a not insignificant portion of that real deal is certainly in the tires IMHO. Those Pirelli PZero Trofeo R tires the Z/28 will be sporting will outclass those Goodyear runcraps on the standard Z06 six ways from Sunday...especially if you want to magazine race against Z06 times that incidentally had 1st Gen F1 supercar tires on them.
Similarly, I am willing to wager that a sizeable portion of the Z06/Z07 performance gain is in those awesome Michelin PS Cup Tires. Nothing wrong with that, its just tires play a HUGE role that really can't be underestimated.
As I alluded to, that 2:58 VIR time was on Generation 1 Goodyear F1 Supercar tires in 2007. You should hear Corvette's chief engineer Tadge Juechter's comments on the vast improvement of the Gen 2s (which are on the ZL1 BTW) over the Gen 1s. In fact, according to Juechter, if Goodyear didn't step up the performance capabilities of the Gen 2 F1 supercar tires like they did, Corvette would have gone over to Michellin tires for all corvettes; instead of just to the Michellin PS2 ZPs for the ZR1 and PS Cups for the Z06/Z07.
So I too wouldn't be surprised that the Z/28 beats a now defunct, no longer in production, standard C6Z06 on whatever track du jour
, but I think the reasons for that will be pretty straight forward when you get down to it.
I'm just glad they are keeping the LS7 around a little longer, that means parts will be available to me longer if needed.
Besides, the C6Z06 is old anyway. The damn thing had a run of 8 model years! You should see how my 2007 C6Z06 stacks up against a 2001 Ferrari 360