code p0300 light stay on. run good going to work 4:30 going home 2:30 on 1998 GMC Sonoma

start missing at operating temp at idol. clean egr rebuilt engine new torque converter,new tran,new distributor,new coil,ignition module,this was befor the misfire hhhhhhelp pSI do not like to process of elimination I would like to pin point it.i think it might be the catalytic converter.give me something to look for. sometime the light flashs then reaching the misfire temp,what do you think. problem every day or every time I drive

Asked by for the 1998 GMC Sonoma
Fuel spider!