Thanks Carl, thought I had done that, but apparently not! My personal problem is clearly memory loss. My X1/9's problem was a bad Bosch airflow meter (AFM). According to Erskine there were three electrical values out of spec, but I don't have more details.
This is the 8th car I've owned over the last 40 years that had Bosch L-Jetronic injection (three X1/9s, three Alfa Milanos, an Alfa GTV6, and a VW Vanagon), and this is the first AFM that's failed. So I'm surprised.
Just filled the tank (after only 170 miles, so not as accurate as running through an entire tank), recorded 27 mpg. Not as good as expected, but certainly better than the 22-23 mpg I had been getting for the past few months before the AFM failed completely.