FIXED!
var base64img='data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAQgAAAFXCAYAAABeLtDdAAAgAElEQVR4Xu19CXhURdb2ISsJgSQ';//shortened version
var data=base64img.replace(/^data:image\/\w+;base64,/,"");
var buffer=new Buffer(data,'base64');
fs.writeFile('/home/engine/public_html/img/base64img.png',buffer,function(err){
fs.readFile('public_html/img/base64img.png',function(err,data){
sendgrid.send({
to : 'address11@gmail.com',
from : 'address2@gmail.com',
subject : 'email with image from base64 data',
files : [{filename:'base64.png',content:data,cid:'1234567890'}],
html : '<img src="cid:1234567890"/>'
},
function(success,message){
if(!success){console.log(message);}
else{
console.log('sent');
fs.unlink('public_html/img/base64img.png');
}
});});});