Altitude Issues 08 X5 3.0

[GrandCanyonx5]

I appreciate all the great post's on the forum and hope to have some insight toward understanding my first X5. We've had Range Rovers for the past 3 models and downsized to the X5. We live at a fairly high altitude above 7,000 feet and the car generally runs fine, hesitation at low RPM began a bit ago. We ran to Los Angeles at sea level 2 weeks ago and the car would barely stay running at low RPM and if I pushed it at all the check engine light would blink and the engine sounded like it was misfiring, the check engine light is now on fulltime. I'd have to pull over on the freeway and shut if off. Restarting it would start and idle fine, then repeat if I pushed too hard. I replaced the battery a month or so ago, new oil and filters about the same as well as air filter. I'd appreciate any help at all, we are 4 hours from the nearest dealer in Vegas.