Alttitude adjustment

I recently moved from louisiana to denver, my truck seems to hate the cold, I was told it can be cause of the altitude. Is there something simple I can do to reset its altitude if this is true? 2000 ford expedition xlt 4.6 in cold weather like now its 7degrees out, it gives me a bad whine when I start it for about 15 seconds and I must keep foot on gas for about a minute for it to stay started. Its only started to do this as winter came in.