Does the Miata have hydraulic tappets, or can you adjust the valve clearances? Your results suggest the possible need for a valve adjustment. IMO, the numbers aren't low enough to be leaking valves, nor did the oil correct the compression to the extent that would suggest worn rings. Plus which I haven't seen worn rings on a gasoline automobile engine in about a million years unless there was no air filter for a long time. (Marine engines have other problems.) Materials and lubricants are pretty darn good these days. Well, I see you autocross it, so maybe you thrash it good enough to wear it out, but I doubt it. How many miles?

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1987 W201 190D