New Cylinder Head? At 48K Miles? What?'04

[Phils]

I took my 2004 4.4 X5 CPO to my local dealer yesterday AM to get a few warranty things done including classic broken cup holder, slightly jarring ride when hitting bumps especially left side. Also I noted the car is rough when started cold sometimes- I included this description in the note to service advisor:

"...2. On starting cold, engine sometimes surges in RPMs. On starting two weeks ago at La Guardia I drove to parking exit to wait in line to pay and while brake applied car surged and jumped forward a few feet….had to brake harder to keep from striking car in front!"

He called at the end of the day and said they needed to keep the car overnight, as they wanted to start it cold. Also the mechanic he said has opened a PMA(?) with BMW on this. OK, no big deal I have a loaner X3 for now. At 3PM on the second day, today, he calls and says you may need to keep that loaner for a while, we think it may be a cylinder head problem and we are basically going to have to replace the head 'essentially the engine' is how he also phrased it. He said they'd confirm more detail tomorrow but it looks like a new head is needed (under warranty of course).
I'll try to get more detail, he had customers lining up, but what's up with that at 48K miles??? Any thoughts or questions to ask?