LOL!, 3 1/2 years ago my car was STOCK, except i had a pod filter, i was running 12psi 0.8-0.9 bar for about 5-10minutes with some SPIRITED driving around. then it cost me $5000. because my turbo BLEW>>>... ($5000 for t3/t4 turbo + full turbo back exhaust & cat)
so yeah not recommended to run 15psi, or even 12psi if you car is stock.
my 2c