1996 Dodge Caravan Engine electrical failure

Hi guys I have one of those famous Dodge grand caravan with a 3.8L Automatic with overdrive it has a enormous 359 000km on it one trany only and a few regular matienace things done to it well now it has decided to have a little bit of a fit that seem to be growing what has happened is when after a long period of driving 3-4 hours striaght it would start to skip buck and cough and the sound of what might be crossfiring. If I would drive the throttle to the floor it would cough then clear and away it would go. Now this problem is starting to happen more often and it has happend at a stop also it seems to happen when driving a slow speed (in town) and driving the throttle to floor does not seem to clear it anymore it will go down to one cyclinder then die if I wait for anywhere around 5min to a half hour it will start and everything is fine. I have replaced fuel pump and filter, coil pack second hand, wire seem ok they don't skip when water is misted over them, I do have engine codes 12, 33, 21 twice, 31 and 55 is there any sugestions other then the code problem that could cause this?