Well, a good starting point for troubleshooting is to actually read the manual and follow the steps in it, you can find the suspension one in this thread:
http://forum.a8parts.co.uk/showthread.php?t=8379
And then compare the factory coding/tyre size/spec to yours etc and make sure its all correct.
There's lots of dodgy VCDS people around that will lower your car with vcds for £80 to make it 'stanced' and all that, and you just can't know what the previous owner's lifestyle choices were
