2016 Audi a6 2.0t can’t rev above 4k rpm warning.

I have a 2016 Audi a6 2.0t that constantly has a 4k rpm warning. For context I had a new engine installed and it runs fine only issue is won’t go above 4k rpm. To which I then got a new turbo because mechanic ruled out that the cause of it was a bad turbo.(and the codes the engine threw were turbo related) After the new turbo was installed the car in continuing to have same 4k rpm max issue. We have since installed new oil pressure sensors,and done oil change. See have the same issues. Any ideas of what it could be. Am completely lost and I haven’t had my car for a month. Need help desperately. 🙏