I have an Avalanche with the STS kit and mine came with the wastgate vented back into the exhaust. With this setup the wastegate was being held shut by the exhaust pressure causing my boost pressure to go up to 10psi. It probably would have gone higher, but I backed out of it. Thinking the wastegate spring was to stiff we switched it out. That didn't help. Finally flipped the wastgate and vented to atmosphere and that solved the problem. Although now it is insanely loud when the wastegate opens on full throttle runs.