My buddy had about the same problem awhile back. Well we started with checkin the electricals, then fuel system, check compression, you name it and was a easy to check thing we did. To come to find out blown head gasket, but not loosing any water no water in the oil, installed new head gasket and she runs like a camp. It did kinda did have a rough idle, but once you hit the skinny pedal it went to SH*t. Try that... Hope i could help man, Im new just tryin to give my  worth