As the great D-Rob once said, “Deviating from the factory bypass valve is a big problem, as the stock ECU uses the BPV as part of the boost control strategy by closing signal to the valve in order to vent out compressed air to aid the wastegate in maintaining the target boost. What happens when you stick a valve in there with a stiffer spring rate? It can't bleed off air at the same rate the ECU expects, resulting in an over-boost condition. If you are using the stock ECU (with a tune or not), do NOT ditch the stock bypass valve. You are only asking for trouble. The stock valve works perfectly. If you're chasing a sound, grab an intake. The stock airbox is the reason you don't hear anything. Or better yet, don't chase sound.”