I recently changed my valve cover gaskets on my 2004 350z to fix the oil leak. After putting everything back together she sounded awful and was shaking on idle. I believe this is due to a misfire but I am brand new to cars and working on them. I replaced both the ignition coil packs and spark plugs, but still no change In the misfire and I don’t know what else do to. Edit: there are no codes showing and no check engine lights

 

Maybe... check the PCV valve on the passanger side valve cover, and the hose that goes from the PCV valve to the intake plenum. Something similar happened to me last month after I forgot to put that hose back on.

 

Make sure you have the coil pack harness plugs connected up correctly. It's very easy to mix-up some of the cylinders (screwing up the firing order) and actually quite common when doing maintenance that require coil packs or fuel injectors to be disconnected. I used a paint pen to label all of mine since the factory harness labels flake off over the years. I hope you picked up OEM coils.
-Icer