So I assume after reading this thread.. that since I have a 2006 4.8is with no aluminum running boards currently... If I want to upgrade to the running boards, I can't buy just the running boards them selves but also need the plastic fender flares that are designed for those aluminum running boards as well? My current plastic fender flares are not compatible with the aluminum boards?

Correct. RB come with new flares.

You can buy the running board kit (for example, the very factory looking one on eBay) and transfer your flares over to the new wheelwell trim pieces that come with the rb kit. It's a little tedious but can be done. It involves cutting little slots in the new trim pieces to accept the IS flares.

The running board, OE ones come with their own wheel well plastic. If you look at the running boards, they transition into the fender wheel arches. These are unique to the running boards. The IS flares can be moved over from your non RB wheel arches, to the RB arches.

As a matter of fact, you cannot buy RB with the IS flares. Those are separate part number, and usually people just swap over the flares from their setup.

The OE kit is no longer available anyway and buying everything separate, cost is around $2500ish for new OE Genuine BMW parts.

Sheesh for 2500 you could almost fly to Lithuania and grab it from the local chop shop and call it "luggage" on the flight back. [emoji38]

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Recently, ebay seller advanation had running board kits that were indistinguishable from oem for $399. Came with the wheelwell trim, etc. Looks like they're sold out for now, but that's the route I would take if looking to add running boards.

Hmmm do they still exist?
I've got running boards and looking for the flares but don't see much around...