street r

Need some advice from people who have actually done it! Twin Turbo car, cant hook at 7psi in 1st or 2nd. Twin turbo 2015 mustang gt. 6r80 trans, 3.15 diff, currently running MT ET Street R 315/50R17 tires. Car is making about 7/8psi at the top end, boost is a little lazy to come on. Running...