2004 Volvo S40 Engine shakes

First do you have the early style S-40 or the new style S-40? Is the CHECK ENGINE light flashing if so stop driving your car until you fix it since a bad misfire will damage the catalytic converter. First thing did you use Volvo plugs or something else? If something else trust me on this one, go get the Volvo plugs. Other brand plugs for Volvo do not work. Second if it is early style 40 check to see he did not cross a wire. #1 plug wire goes with #4 coil and #2 wire goes to #3 coil. If that is ok remove the 2 coils and inspect the boots. They usually split down the sides. If they are replace those as well. If all that is good and you have the Volvo plugs installed and it still misfires then I suspect the the capacitor inside the harness for the ignition coil connectors has gone bad. Would recommend you replace that if everything else is good. If you have any other questions let me know.