common issues with 94 century

I'm sorry to say that -- this car is 26 years old now! Anything goes, really. You can't look at "common issues" when a vehicle is of this age; there's no way to know what is going on without hands on testing that will evaluate fuel delivery, ignition spark, air intake, emissions controls, engine timing, engine compression. It appears you've done a lot of parts replacing, but maybe no troubleshooting? Testing will be quite helpful. https://repairpal.com/repair-shops

Professional quality scan tool is quite capable of testing this 1994 vehicle - SCAN TEST is highly recommended.