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Boost Drop?

'01 A6 2.7T 95k…Not boosting as high as normal…the check engine light came on the other day, P1136 code said engine was running lean. I found a small vaccum hose leak near wastegate and fixed it today (CEL is still on though). Stock boost is normally around 8-9 psi, but I am only getting 6-7 psi. Also, the boost seems to climb more slowly than it has been, and it occassionally goes into limp mode (only 3-4 psi). The turbos were replaced about a year ago with all new blue hoses. There arent any other symptoms, no weird noises. Any ideas?

A couple of things to look into. Are you running premium gas? On regular the knock sensor could be detecting knocking and not allowing full boost.

Another possible is the wastegate(s) might not be working properly due to carbon build up, or sticky valves in the mechanism. After opening if the wastegate(s) don’t seal well you can’t get full boost.