1989 Pontiac Firebird

My stepson bought a 1989 Firebird and took it to a shop for a checkup afterward. Since then the garage has cleaned him out with one new problem after another. I drove the car about 600 miles without any difficulty (it felt like it needed a tune up and the gas line cleaned). The garage that has been holding the car hostage is now telling him that he needs the onboard computer changed. (I didn't even know the computers were that advanced in 89). Anyway, apparently now if he wants the engine to run, he has to keep his foot down on the accelerator. If he takes his foot off, the engine dies. That sounds more like a fuel/choke issue than a computer issue but could use some help in diagnosing.