i'd start with the easy stuff.

pull code if efi, check cap and rotor, plugs, wires, maybe even do the vaccum test for the egr if its just stumbling. i was driving down the road, and a bad rotor caused my truck to buck so wildly that i could not drive it, finally it got to where i could not even start it. this happened over a 10 min span. spent 50 bucks and a day towing it. ended up being a 4 dollar rotor.

could be alot of things, give us a better discription of ehats going on.