The post above brings up a good point, check the simple stuff. In this case, you can watch the built in diagnostics to see what gear it is in, as well as most of the sensors. You should verify actual fuel pressure, verify the quality of the spark, check the ignition module for a sticky ooze if it is the original Magnavox style. Verify throttle position sensor and ignition timing in diagnostics. All that info is at your fingertips from the drivers seat. Catalytic converter replaced but was the intake system checked in smog inspection?