If it truly is meant to be the sustained boost number for warranty, then so be it... I just know that when I was spiking to 28psi that I was clearly told by my tuner that it was not good, even if momentarily. We all know a stock turbo with stock wastegate can't hold more than ~23.5 psi through the powerband anyway, and it also spools near instantly as well, I just don't see why you wouldn't want to stay within limits for peace of mind when there is no performance benefit otherwise.
