I checked my TSB & PROM ID manual, all I've found is one TSB for plugs, the rest are nonsenseI promise everyone a full photo dump ASAP. You're absolutely right: the 1991 model is hands down the most desirable of the series, which was a huge factor when considering the purchase.
Had it been anything earlier, I probably would have passed for one reason: TEVES brakes. The '91 models, with their conventional vacuum brakes and Bosch ABS module are far more reliable, save the one year only ABS sensor's up front.
The tricky thing about owning a vehicle such as this comes down to the multitude of unique (AKA irreplaceable) components. For example: the windshield for the Reatta has long been discontinued. From what I've read, assuming you can find a donor car and a glass guy capable/willing to R&R a used windshield, it's a $2k+ repair.
Same goes for the rear struts. Monroe, the sole remaining supplier, discontinued the part a couple 2-3 years ago. So far, there is no viable alternative.
There's one for a shorted IAC motor, but if your car idles, I doubt that's a problem
This book goes up to '92, I've got up till '96 somewhere around here
If you want to see if there's a PROM/MemCal update, send me your ECM info and I'll check it against the book