once i got the car fixed and out of safety boost i was at 14 psi. with sp500s i took it to 17psi jets but the car with surge and blow off crazy. i swapped out those BOVs you have in your picture with some SSQVs and fixed the issue. so heads up those old HKS valve may only work up to 15psi, im not sure if its the design of the valve or defect in mine.