so it sounds like a fuel starvation problem at low rpm? i had one eat its into the fuel pump cam on the front of the camshaft. at low load or higher rpm it would pump enough but under load or lugging up a hill it would do the same thing it was on a 87 flat bed ram dumper used for constuction. not sure if it is the same problem but it sonds like it?

2013 Chrysler 300 touring 1974 Dodge Charger SE. 360-727-8.75-3.23 sure grip 1972 Dodge Dart Swinger 1995 Dodge Ram 1500 4x4