Cool rule of thumb for figuring ball-park 0-60 from hp and curb weight.
0-60 = 1/2 * curb weight / maximum horsepower
x = 1/2 * 2860 / 177 = approx. 8.0 seconds.
5.4 = 1/2 * 2860 / y hp -> 265 hp
Of course, these are just approximations, but it does seem to suggest what we all suspected - there's pretty much no way the 5.4 second 0-60 figure was for the base Solstice.