I felt no difficulties what so ever.... Had normal super petrol fueled into my prado.... No problem what so ever... on the Peak of Pirchanaasi Mount Behind the tourist Point it was 3760meters max on the Altitude meter... I havent got the Pic...
Regarding 16400feet so thats correct ... It is highier then Khunjarab paas... Khunjraab paas is a paved road while where I went In Naltar wasnt... it was a Just a series of high hindukash Mountains I was driving on it in much severe driving conditions then the Pirchanasi summit in search of the Ski point...
Breathing wasnt mentionlably difficult or hard .... yes it was a different feeling then normal... the altitude at unknown Mountain paas was 5380meter so calculated it roughly in feet...