You changed your iridium spark plugs after 115k miles now your engine shake and sputters?

perhaps you connected your spark plug wires incorrectly check your firing order if you crossed a couple of spark wires the engine may still run but very roughly also you may have spark plug wires that are not fully connected to the plug are you reusing the old plug wires may be time for a new set check connectors for corrosion recomend using high quality spark plug wires