I like the felpro rubber gaskets, run away from the cork gaskets theyre terrible. If everything is good under the covers I would next look into the lifters.
Ive done this to clean up several dirty engines, and do it occasionally with oil changes to clean up sludge and carbon but I like to drain the oil and fill the engine up with five gallons of clean diesel. Leave it in the pan for 15 or so minutes and drain it. Youll be amazed how sludgy the diesel looks when you drain it, and it really helps clean up long term deposits, run MMO in it afterwards and cut your oil change intervals in half for a few cycles to see if you get an improvement.
Ive done this to clean up several dirty engines, and do it occasionally with oil changes to clean up sludge and carbon but I like to drain the oil and fill the engine up with five gallons of clean diesel. Leave it in the pan for 15 or so minutes and drain it. Youll be amazed how sludgy the diesel looks when you drain it, and it really helps clean up long term deposits, run MMO in it afterwards and cut your oil change intervals in half for a few cycles to see if you get an improvement.