There is no testing available as such. This is why I said open it and wiggle it a bit or put a piece of tree twig under it in different places, while your key is in the ignition. You will here your pump going on and off. When you find the proper position for the twig (pump will start humming) you are in the right spot and so the ECU connects properly and you can drive with the twig for months to come. It is very very unusual that the pump went bad. In VWs and AUDIS they last 30 years or so. I am guessing that the mechanic was not appropriate for the job. I just can't see the pump needing replacement for my 35 years experience with these cars.

 

The pump is good. Just replaced a couple years ago. Btw there is nothing holding down the ecu. The clip is gone.

 

Cut some rubber hose and insert it between the ECU and the box that holds it so it sits firmly, but is still elastic to a degree.

 

OK I'll try that. How is all this connected to the ESP and the misfire issues?

 

The internal connections in your ECU are damaged or disconnected. You can not see it with naked eyes.

 

Should I replace it?

 

Yes if you have $800.00 for the used one or $3,000.00 for a new one. Write the number from ECU and when replacing get the same number.

 

I can get the exact same number ecu 8EO 909 518 AF off ebay for 230 shipped. Are those prices you posted including shop labor?