My engine has stalled several times in high altitude. It starts missing and black smoke comes out.  Sometimes it quits completely and sometimes I can feather the gas pedal and it will slowly work out of it. After shutting off, it usually starts..  I have installed a new air flow sensor in the air cleaner can.  I have had two mechanics put it on their computers and nothing shows up.  I have also put a new fuel filter in it.  We have not driven since I put in the new air sensor.  We are getting ready to drive over Vail Pass so I hope it works.  Does anyone have any other suggestions?S