Do you have a P0299 underboost code? This is probably the reason why, the wastegate lose its strength and function. We’ve seen it on BMW and Audi cars quite often. The only fix, is a new turbo. Much like this 2011 Audi A4 Avant is getting now. Reach out with questions on your turbo application if you are seeing the same issues. We’d love to help you out! | Eurocharged Minneapolis