This is a page from a recent emissions test on a 1990 LS, 5 spd. No EGR on this model, AFAIK.

It has less than 70k miles, but was basically parked for several years before I started working on it. Engine runs ok at idle and at steady speed, and a little rough on acceleration. The cat converter is probably ok at this mileage, other emissions related components have not been checked yet. I am courious if anyone has a good idea of where to start looking, w/o throwing too many new parts at the problem.

The graph shows the engine runs way too rich on even moderate acceleration. HC emissions exceed the range of the test, and NOx is not far behind.