Wouldn’t it be worth removing the spacers for a trial period, that must be having an impact.
I can't for the life of me understand why you have carried out all this troubleshooting when there are aftermarket parts fitted? I would have thought both Audi and Pirelli insisting the car was at a completely stock setup? Having spacers fitted surely makes all the testing is null and void regardless of what the alignment reports suggest?
Did Pirelli do all this free of charge? Has Audi had your car back and forth free of charge under warranty too? Were they both fully aware there were spacers fitted?
Billy, you have no chance with aftermarket wheels, spacers and PS4's, I wouldn't even bother wasting my time if I had your setup.
I've got mag ride but no spacers (yet) and had the same issue, so I'm not sure it could be the spacers.