ive researched this and can't get my head around how to fix it.
My 2004 A4 1.8t (no mods) On cold starts, my secondary air pump makes a loud noise like a jet engine- this continues for about a 1-2 minutes and stops. After a couple minutes of silence it starts back for another 10-30 seconds and stops until the next cold start.

The code is P0411- insufficient airflow.
I read about this and the listed culprits are the pump, combi valve or the plastic hoses extending from the secondary air pump?
I replaced the combi valve and the CEL came back on. The noise hasn't stopped on cold starts. The plastic hose going from secondary air pump to combi valve isn't cracked or broken (took it off and checked- there was water here, which is why I replaced the combi valve. Read that bad combi= condensation and water into the pump), haven't taken off and checked the plastic hose leading from the secondary air pump to the air filter. The pump works since I hear it screaming.

Thoughts? Opinions?

 

Here's a video if it helps!
This video isn't of my car, but it's the same issue with the same noise - only difference is the make. Start video at 2:30 -