Yes, we are assuming the blood in the vomit is from irritation, either from barfing repeatedly or from an ulcer. The vet suggested endoscopy, but at $2-3,000 for something that might very well not produce any real answers or solution, unfortunately that is just not going to happen. 
Trying a grain free food is an interesting suggestion (although I have to say, all our cats are doing very well on the Hills c/d - shiny soft coats, firm compact stools, etc). I will look and see what is available around here (remember I am in Canada) and maybe try something along those lines.
It's not clear to me exactly what Mo's deal was when he was at the shelter. He either came in with, or immediately contracted, a very serious URI and spent a couple months in the cat supervisor's home in intensive care (he has minor residual 'chronic URI' still, just the very occasional sneeze and tiny bit of dark nasal and eye discharge, especially after he's not eaten for a few days). So she had difficulty getting him to eat well during that period but he had a logical reason for it. When he got better he started eating ok but according to her did not eat a large amount (this does not match my experience with when he's being very 'eaty'). It was cheap kibble tho. 
He was actually at the *shelter* (as opposed to in her home) for about a month before we adopted him. But, because they have a dozen or so cats per room (no cages, all together -- yes, the shelter quarantines them for I think a month before putting them in there) there was no way to tell how much he was or was not eating. He seemed happy and bright there, though, although a few sneezies and eye boogers.
I wonder sometimes how many homes he's had in the past, if maybe he's done this with previous owner(s) who finally gave up and opened the door and let him out and he wandered off 
		
		
	
	
Started work on the second compartment of the cat enclosure -- a 10' long enclosed bridge, about 7' above the ground, over to the cedar hedge, where it will eventually connect with more.
Pat