My '91 buick Park Ave. 3.8 will not start. What could be wrong any ideas?

well at first the car would die in park. then after driving it more it would die while driving. then we would get it back and it does not start while hot it turns over and it throws no code so here is what  was tested, tried, and replaced......the ignition module tested, coil pack tested, fuel injectors tested, fuel pump tested, battery tested, plugs and wires replaced, crankshaft sensor replaced, pcv replaced, air filter replaced, tried a different computer and yes switch the chip from mine to new computer, cam sensor was replaced 2 months ago, ignition switch replaced last fall, harmonic balancer replaced last spring and tested it. been talking to mechanics all day. a couple even looked at it and tested a few things themselves, mainly jiggled wires and checked a few vaccum lines. any thoughts on this one??