I guess ill throw my opinion in this thread. Ill start off by saying stick to the basics Air,Fuel,Spark(timing) It never fails. To me it sounds like you have a timing problem. That being said I would check everything timing related like CKP, CMP, Ignition Module, Coil Pack, and ECM If you haven't already.
Maybe even sound check the injectors for the "click" to make sure they're firing.
But considering i have been through weird situations myself , i would check the ECM or your PROM chip for smells, acids and anything strange. I personally have witnessed things happen over night.