I got around to removing the exhaust manifold heat shield, to anyone reading this in the future removing the bolts for the shield is a lot easier than you might expect, even if they are rusty like mine were.
I found what I believe to be a hairline crack between cylinder 2 and 3.
Photo 1(as close up as I could get)
Photo 2(more complete photo of the crack)
Photo 3(close up of crack from different angle)
Photo 4(zoomed out to provide orientation in engine bay)
Link to complete album
Is this a large enough crack to be the source of my engine tick?