Thread: poor AFR sea level

This weekend I'm goin to the beach and when I went down to the sea my car started to fail and my afr go to 16,17,18 --- very poor this without boost, if i give more gas my afr is better but still poor I not understand why this happens, someone has a theory?
I'm usually at 1400 meters above sea level.
My car is a B13 odb1 whit basic Calum ecu.

Thanks.