I have a 03' with 5300 Vortec. I am in Central Texas at about 650' and go to my place in Colorado two or three times a year. Truck does great at home and usually does fine in Colorado above 8500' but when I leave I start to have stalls and truck will not start but eventually does. This has been happeing for about 4 years now. Only thing I can think of that are different is using lower Octane gas while up there and then dropping in elevation and a rise in outside temperature. Last week while up there I started having same problem while at altitude and had it most of the way back to Texas. Any ideas?

 

Sounds like you have a component bad in your emissions system........O2, MAF, ect.....the only vehicle that should have to be "reset" for diffrent altitudes is a diesel