Yup, distributor with electronic module is a common thing with the TBI vehicles. Last week I amazed a good friend by resurrecting his v6 Silverado. Same random behavior as yours. His wasn't as far gone as yours, it would usually start up good in the morning. Once it warmed up a bit, no bueno...
I've had a few vehicles where either a precat or main cat disintegrated and clogged up the stuff downstream. My 94 Sierra is starting to get that way. Previous owner had a single to dual muffler and tailpipes done at the muffler shop. I can hear the main cat rattling, and the donut gaskets on...