It is not like the old days, where oem tires were as hard as iron to ensure people wouldn't be pissed off replacing them in a year. These days it is not uncommon to find oem tires MUCH less durable than the off-the-rack version of the same tire, in performance applications.
It isn't a big deal to change compounds and these MOs were designed for AMG Mercs and such. It's my opinion, these soft Pirellis made up a good part of the reason the Mustang fared so well in mag tests.
2014 Premium GT, SGM, Brembo, Auto, Tech, Comfort, etc. GT500s, Steeda UCA, VMP auto tune, 100 shot on BBR tune, best et: 11.38 at 120.85
2012 GT, Candy Red, Brembo, 3.73, Tech, Comfort, etc. Procal tune, Roush upper, UMI LCAs, Steeda red bracket, GT500s, 28X10X16 Hoosier slicks, best et: 11.91 at 115.23 RIP