Great story ... I love those "free visits" to the shop (had one myself just this morning).
It's somewhat related, and as a favor to any "Googlers" who happen by, I just got rid of a "rachety racket" I thought was coming from the engine top. I've rescued a '93 XR2 from the nursing home (so to speak) and had a general check and welfare shop visit.
Immediately thereafter I had an oil change from the local "quick lube" joint with synthetic 5W-30, and driving 15 miles home heard what sounded like broken lifters or valves clacking LOUDLY ... accessorized by smoke (in retrospect, this was actually just a little oil change slop on the exhaust manifold, apparently).
Further investigation showed that the noise didn't seem to be a problem in 1st/2nd gears or when the clutch was depressed; we found the gearbox almost devoid of fluid.
60 miles on it today and no noise.