Justin, try loosening one high pressure fuel line at a time. This are the six steel lines from your injection pump going to your injectors. If the engine quites down when you loosen a specific high pressure line, then you know that your problem is either on a bad injector, or on the injection pump.
You can have the specific injector checked, and/or also have a Bosch injection pump mechanic replace the six delivery valve copper washers on your fuel injection pump. This type of work is relatively easy, and can be done on-engine without dismounting the injection pump.
I hope this helps.