any quality HID kit will not change the projection pattern of headlights (at all). cheap HID kits that use universal capsules instead of ones with correct focal points, however, will.
You will always get better light output if you retrofit a projector headlight. You can just buy ones from a premium package car that had factory HID's.
I believe on the e90 you will need to code the HID function for the OEM hardware to work correctly.
i believe you can retrofit the LCI headlights, but i'm not sure as i dont have an e90.
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2002 TiAg M3 6mt
deoranged, dechromed, led tails, ZHP knob, UUC SS v3, GROM, OEM 220M 19's, Michelin Supersports
2006 YZF-R6, bunch of go-fast stuff