1995 Mazda millenia full tank of gas but says empty with light on already replaced fuel level senders instrument cluster still reads empty help?

You've got to drop the tank and replace the float that's the part that tells the light when its full or empty....if that doesn't work then replace the gauge sending unit...if that isn't it then check if the light is what is bad replace the light...if that doesn't work then i don't know !!!