hello everyone

my name is Michael and i`am Mechanical Engineer

3 months ago i buy a 535d 272hp (non facelift) and i have the following problem

i do a log with 4th gear from 1600rpm to max rpm I discovered that between 3200 to 3600 i have 200 milibar loss of boost

by now i changed:
-all vaccum hoses
-tested vaccum leak
-both pressure converters and electrovalve 11747796634 11657793032 11747810831
-tested for vaccum leak all 3 actuators

I lost all the ideas and car still have this pressure loos and from my point of view is from transition between small and big turbo

click on the link below to see the graph

https://ibb.co/jiCUcy