Potential turbo or waste gate issue?

I have a 2008 Octavia vRS with the 2l petrol BWA ea113. Around 8 months ago, I upgraded my air intake from the standard engine cover style to a Ram Air brand, cone style kit. All has been fine until a few months ago. There is a bung (pictured) used to blank off a section that’s not needed for the Octavia.

 There is something that is causing this bung to pop out. Something that I think is causing back pressure in the induction pipe great enough to force it out.

I haven’t heard anything that would be an obvious sign to look at first. But with that being said I have heard compressor surge sometimes when coming off partial throttle. Usually can occur when changing from 1st to 2nd.

I can tell when the bung has popped out when I put my foot down and the car fells ridiculously slow. Pop the hood and the bung is gone. Replace it and all is good. I’m now on replacement bung number 3. 

Any one experienced anything similar or have any leads on what to investigate?

 Thanks 🙏