I recently bought a 05 legacy gt. It was stage 2 when I bought it. Catless down pipe, after market up pipe, full Cobb intake including intake Manifold , Cobb access port and straight pipe exhaust. It ran great at first. Now it is sputtering real bad around 5 psi. I took it to a shop and they can’t find anything wrong with it. I have seen on some of these forms that a lot of people have had this problem with stage 2 but not any Solutions. The only code on the car are about the manifold. I’m wondering it that’s not the problem. Anyone have any thoughts or advice? Thanks