1997 Chevrolet Malibu random cylinder misfire

I have a random cylinder misfire taking place in a 97 chevy malibu. I have replaced the crankshaft position sensor, both o2 sensors, plugs, boots, both coil packs, MAF sensor, Throttle body sensor, Oil Pressure sensor, fuel filter, injectors. Everything is brand new, I am unable to track down the cause of the misfire. I took the car to get smogged at a STAR smog center and it PASSED. I never would have thought it would pass but it did. I reset the check engine light before going and it passed all tests. After leaving I can again feel the misfire and after a while it will become a catalyst damaging event. Please help.