Quattro and FWD springs are different i believe due to the extra weight in the AWD car. Really not worth doing this mod anyway if you will be changing the springs in the end anyway. They will barely be noticable.
How do mate ! i am on about doing this,is the ride still better on the 30mm drop springs than it is on the standard s-line suspension? i know the lowering springs are progressive so i am hoping not but also i have the same wheels as you which i intend to keep for now,have been offered some genuine Rs4 style one but there still the same as in 18's and not to offend anyone without trying them on the car i still like mine better unless anyone can point me in direction of someone who has them on there car and can see there pics