So I am hoping to change the game such that
Only river/lake/oasis/coast/ocean..etc and cattle/wheat/banana..etc gives FOOD (more than original)
While any other tiles gives no FOOD


I changed some yield number in CIV5Features.xml CIV5Terrains.xml, and indeed they are working.
But,

1. City auto tile growth doesn't know to choose these water tiles over the vast empty plains. I suppose <InfluenceCost> negative will help but I can't seem to add such node to river tiles?

2. Does AI choose city location by the yield numbers or by some other heuristics that I have to edit too?