Hi.
I will check my ballast that was taken out a H7 HID kit i was supposed to use for my C4 S6 so we can see the voltage and stuff
But since they sell D2R/S bulbs in almost any HD KIT i would guess that the Ballast is the same.
Only difference from the oem setup is that it might use a second longer to heat up the bulb when starting. I have not noticed it but from having aftermarked HID in cars earlier this is usually normal.