Turbo plumbing help

I am building a 06 gto ls2 twin turbo for a freind.  just have some questions on the intecooler plumbing.  We are going to be running 10psi of boost,  he has two HKS ssq3 blowoff valves, 2 garret gt3582r turbos, with presion 46mm wastgates.  Where would you run the blowoff valves at befor the intercooler or after? Or would u just run one blowoff valve before or after the intercooler?  And the wastegates are set at 15psi of boost do i need to change that also?  Hope I can get some help>