Audi A4 B7 2.0 TDI BRE Engine Boost issues

Hi everyone, this will be my first post on the site so thank you in advance to anyone who can help.

My car, a 2008(57 plate)Audi A4 Avant B7 2.0 TDI with engine code BRE. I'm currently facing issues of boost/air flow issues.

Issue:
With All electrical sensors connected, the car is extremely underpowered, however does sometimes(unable to replicate) spring back to life and have full boost.

What steps I've taken:
I first purchased OBDEleven pro pack, I was using this to clear codes and see live data. I could see, using live data, the boost pressure actual and specified. When the car is not working correctly(issue above) the specified boost pressure remains sort of capped, no matter how much I put my foot down, it hangs around 1570mBAR and the specified follows suit. When I let me foot off the accelerator, the specified goes down as does actual. However when the car springs into life, now this could be at any point at any throttle position, the specified will increase as normal as will the actual.

Now, I've also looked at the MAF sensor readings and found the, when the issue is happening, the MAF sensor live data appears capped, same as the boost pressure. Same again, when it springs into life, the MAF reading shoot up in a normal manor and the car pulls away.
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With the car being fairly dangerous being how slow it is when the issue is happening(90% of the time) I decided to unplug the MAF sensor, this would also act as another test. The car, with the MAF unplugged, works fine, boosts fine etc etc. It does run lumpy and not as powerful but this is to be expected, the key point I'm making here is that the car boosts and responds to my inputs just fine with the MAF unplugged.

I have tried 1 new MAF, cheap one, and 3 used but tested and working Bosch MAF sensors, the issue is still present in all tests.
I have tried a new MAP sensor, same issue.
The EGR is blanked off but not mapped out. - - - I have a new remapped ECU which I need to install but wanted to get this issue sorted first

I have just bought a Bluetooth multimeter to test the wiring for the MAF sensor with some wire piercing probes. The reason for the Bluetooth is the car appears fine at stand still but the issue is present when driving so would be good to see MAF voltages when driving.

Forgot to mention, no fault codes are logged when the MAF is plugged in. Only one that comes up is the EGR fault which is due to it being blanked off.

I will get a video of the live data and show what I mean because I don't think I explained it well

Thank you! lots to try there. I will get back in a could of days with the results.

Thanks again

Got some good news. I read everything you said and decided to tackle the easiest things first. You mentioned about the actuator for the EGR valve, I didn't know it had one, I thought just a blanking plate and call it a day. That being said, throughout all my testing, that has been one thing that hadn't changed. I decided to go out and remove the blanking plate(Engine was still hot so burnt my hand ), cleared the codes and took it for a spin. The smile on my face when I had consistent boost and live data readings.

It does beg a question though. How do I go about blanking the EGR then? I want to keep it all there for whenever I sell the car but would like to use the blanking plates. Do you have a picture and possibly instructions on how to remove/disable the actuator and prevent this issue from happening again?

Thank you again for pointing me in the direction, it has lifted a weight off my shoulders since this has been going on for over a month now.

I will still be doing all the cleaning etc just wanting to know how to do it properly. Thanks

Yes, I got the ECU with DPF and EGR removed. Just messaged the guy, he said blanking plate will be fine as the ECU will not request the valve to open at all. Seems like the problem will be sorted and EGR blanked.

Going to order new gaskets and will get the intakes cleaned.

Thanks again for your help.