90 Chevy Celebrity losing acceleration and sputtering

My 1990 Chevy Celebrity (station wagon) has two problems and I’m not sure if they are related. The first occurs while idling at a stoplight, the car will sputter until it cuts off, unless I give it gas. The second problem happens at higher speeds. The car will suddenly not accelerate when we hit the gas. It happens for a few seconds, and then normal power resumes. Nothing else cuts off when this happens. Mechanic has changed fuel filter, tested fuel pump and relevant sensors, checked ignition. His last resort now is a bad computer. (The service engine light has come on a couple times, but left no code.) Any thoughts? Thanks in advance!

On a car this old, there could well be multiple problems.

The problem while idling could be the result of a bad Idle Air Control (IAC).
The acceleration problems on the highway could be from a bad Mass Air Flow (MAF) sensor.
A gummed-up or worn-out throttle body could also be to blame.

Before you go to the expense of getting a replacement computer, you should have a mechanic (possibly a different one!) check the items that I mentioned above.