Well, the problem there is "pretty much" ain't "good enough". Have you got the head off yet? Hopefully something obvious will jump out at you. I'm lazy at back reading. Is the sleeve in #8? If so, that would be HIGH on my list of suspects.
Ok, I back read TWO posts and see you have the head off. lol If nothing obvious, I would be really leery of #8 if that's where the sleeve is. You can still have it pressure tested, but at this point, it will need to be a bare block to get that done.