in the appropriate lamp codes (for halogen that would be leuchte6 and leuchte7, modify the dimmwert value to 80 or so (stock for halogen is 100, iirc, 127 is full-bright). Changing the lasttyp (lamp type) to xenon is also useful to remove flicker/error codes from bulb check. Not a 100% solution as even very cold starts can cause ballasts to throw an error every now and then.
Oh, Mine is on 127, i hope reducing it wont affect the output too much.
I Tried changing it to Xenon Abblendlicht And it threw an error, Something about can line 3 and 4, this setting is probably for OEM Xenons.