can't you say, "Mi venas mangxi" ?
Por is used to state that "manĝi" is the reason for you coming.
"Mi venas manĝi" is accepted (23/7/15)
What's the difference between "ol" and "por"
"Ol" is "than", "por" is "for".
Can we say "mi iras por mangxi"?
but "iras" means "go"