I have a leak from what looks like the driver's side front of the head/block area. Car is a '92 with original 120K mile, unopened engine. Turboed for the last 15K miles. I did a timing belt, seals, etc, a couple weekends ago and cleaned the entire block with about half a case of brake clean to ensure I could see any leaks from the front cover and valve cover gasket. I also changed the CAS o-ring. Valve cover gasket has been clean as a whistle ever since, nothing down the back of the head/block from the CAS, and I had the valve cover off yesterday and it's dry under the front cover.
From what I've read in the last hour or so the head gasket can leak oil sometimes and that's what this looks like to me, but I'd like some opinions. Joe started a thread
about this a long time ago, and Hustler said he had a leak in the same place where I suspect mine is weeping, but there was no followup from him (Hustler). I've not had a Miata head off, but I think there's an oil galley in this corner, circled in red below (random pic, not my car).
Here are some shots of that location on my own engine. The first couple show what looks like gasket material poking out, which I removed before the last two. Note that the head and back of the TB area are relatively clean and dry compared to the wet oily slick starting at this corner and trailing down the edge of the block.