[Paul.y]

A while back my 335i peak boost started getting lower and lower. I own a 2011 e90 335i which is fbo and mhd stage 2+. I usually peak at around 18-22psi boost. I noticed that it felt like I was underboosting so I monitored my boost with mhd and it would peak at around 17psi. Over the course of a couple weeks the peak boost would get lower and lower until it wouldn’t go over 10psi. Also, I would be getting the following 2 codes along with a “Engine malfunction! Reduced power” message if I tried to push it over 10psi.
2906 - Intake plenum: Suspicion of leaks between exhaust turbocharger and intake valves.
2774 - Air volume, plausibility: Air volume too high.

I checked most fittings on charge pipe intercooler etc and eveything was fine. I tried pressurizing the system from the intake and spray water on fittings and such to find air leaks that way and also found nothing. I did my research and I found that my vacuum reservoir might be internally cracked and if it is there would be oil in it and in the line going into it from the vacuum pump. I checked and turns out that some oil collected on the bottom of my vacuum reservoir. This led me to replace the valve cover. Upon replacing the valve cover, I still had the same problem. I then did a cigarette smoke test (which I probably should’ve done before ordering a new valve cover) and found that smoke was coming from around the vacuum pump area. I did a lot of research and the only thing I found is that the diaphragm on the nozzle of the vacuum pump can deteriorate over time. I purchased a new diaphragm and when I went to replace it I found the old one was destroyed into a bunch of little pieces. However, once I replaced the diaphragm the same exact problem persisted and I would still peak at 10psi boost. Boost builds completely fine until around the 10psi mark then I hear a wooshing sound and it throws engine malfunction message and the 2 codes. Also, the idle is very rough and when the engines cold it has stalled several times on its own. Do I need to replace my vacuum pump entirely or could it be something else? Thank you for any help.