Here is the end of the story. Dealer said different sates have different situations, no dealer in Houston area gave extra discount other than the $4,500 eco credit, I got $500 it was a "good " deal. And they personally don't trust any dealer in Eastern coast or California would give $8,000 off MSRP, unless they see the paperworks.
I don't believe the **** but consider I will go back for service in the future, I don't want to burn the bridge, and my CA doesn't look like a bad guy in my purchase, so I gave them 5. As exchange, they got me a X5 car cover ($260) and a BMW bear ($30?), they also told me the window tint and floor mats are courtesy too.
Anyway, thanks everybody and hope you guys have a merry Christmas and happy new year!