Yes, it is your SAI pump failing-secondary air injection. It is emissions related. Your car will run fine without it functioning properly. Best bet is to get a used one or on the Web there is DIY on how to repair it.
I figured I'd start in this section, here goes...
I just started a new job which results in a new commute (about an hour).
As of late, while driving my 2003 a4 1.8t has been making this ear piercing, high pitched noise that doesn't go away until I shut the car off. Its doesn't make the noise on startup, only after driving a while.
The noise stays at the same pitch and does not change with rpm. The pitch remains the same while at idle or @ 75mph on the highway.
I've checked under the hood several times in an attempt to identify where the noise is coming from but its so damn loud that I cannot even guess where its coming from. Also, the car continues to run and drive fine.