A search, (yeah I know) revealed that P1179 is usually caused by a clogged fuel filter. What appears to have been the original AC Delco filter was indeed so plugged I could barely blow air through, it's a wonder the engine ran at all. I installed a fresh Fram filter with zero flow resistance and not surprisingly the surge of fuel flow and pressure flipped the code to P1180 Maximum Positive AMFR. I let it settle down, drove a few miles, stopped and restarted, then cleared the code. Presto, no reappearance. Lesson learned, replace that fuel filter regularly.