Ok so I understand mostly how a turbo works but I'm a little confused where to start and how to troubleshoot this issue correctly. I have an 08 r56 that has the stock turbo and tune. I have rebuilt the engine and have modified the car substantially. My question is this. When I'm driving the boost will hold at around -11psi until I hit the accelerator. At that point the psi will go to near 0 give it take and not have the power it use to. I have so far checked the hoses for leaks and nothing I'm now cleaning the k and N filter to see if that helps but I doubt it I have no cel for this. I've read it could be the bov or wastegate. How would I best diagnose this? Also with this turbo having 160k on it I don't mind ordering a rebuild kit from gpop and taking that off the list as it probably is over due anyhow. Thanks in advance for any assistance.

I also removed the inlet hose and felt the turbine and no slop in it.