Hello everyone
I own a 535D 272hp
I did a log with 3th gear from 1600rpm to max rpm I discovered that between 3300/3500rpm Ihave around 400 milibar loss of boost

at 3000rpm car makes 1.8, when reaching 3500+ rpm boost goes down to 1.4, then towards the limit is getting to 1.5/1.6

by now i changed:
-all vaccum hoses
-tested vaccum leak
-both pressure converters and electrovalve
tested for vaccum leak all 3 actuators
-Map sensor
And made a smoke test 3 times, no leaks

Things I have upgraded/modified:

Bigger Wagner intercooler.
Sport cone air filter.
Unplugged egr vacuum and put a bolt tu the vacuum line( the EGR is closed)
[the software is stock]
[Dpf is healthy]


I took the turbos off, I have checked Bypass plate, is okay , it opens and closes smooth.
I checked the wastegate on the turbo and is good, no wiggle and not stuck.
I checked the switchover valve, it closes and opens smooth,
I have changed all the orings from turbo side til the intercooler.
Same result


I am dealing with this issue for 3 months, can somebody please help me?
I am going crazy with this car