Use to have exactly the same problem about four years ago.
The cause was a defective throttle position sensor.
That TPS is simply a potentiometer linked to the throttle. It tell the computer how much throttle is applied at any moment.
Mine have a small crack in is resistive band. So when the cursor reach that exact point, the TPS send a zero-volt message and the computer react by decreasing the amount of fuel.
I simply change the TPS (take about 3 minutes! It's a modular component with simple solderless plugs) and it run just fine now. A new TPS worth about 150$ but I manage to find a used one for 50$.
I've seen on some other forums than that particular problem is very common in '90s zukis.