The car in question is my daughter's '90 244 DL, 170K. Lately, it has been idling roughly, hunting/pulsing from about 750 rpm to almost dying, and sometimes dying altogether, at which point "check engine" light comes on. LH 2.4 OBD is giving me codes 1-1-3 (fault in fuel injectors) and 2-3-2 (fuel system compensating for rich or lean mixture at idle).

Throttle body is clean, and there are no vacuum leaks that I've been able to locate. IAC motor recently pulled, cleaned and oiled per the Foster method. TPS adjusted to "click" when throttle is closed. Resistance is 16.5 to 16.7 ohms on all four injectors (spec is 16.0). Car runs fine at highway speeds. Substitution of a known good AMM had no effect. Codes can be cleared and car will run fine for a few days, then go back to the hunting idle and dying routine.

Am I looking at the beginning of the dreaded 561/951 ECU failure here, or overlooking something obvious? (and cheaper!)