Engine shaking at idle.

[NobleRogue]

If I were You I would start by testing my Mas Air Flow Censor and Throttle Position Censor. I would also check to make sure all of my hoses were properly connected to the Air intake Tube as well as to make sure that they were in good shape and fitted to where they should be without leaking. In response to the leak down test I would do a Carbon Cleaning with SeaFoam before anything else exhaust related. www.youtube.com/watch?v=AW5Rf1Wg-Vs . This is a helpful video on how to do this. Buy two cans of SeaFoam. one for the intake and crank and the other to be added to a full tank of fuel. If the SeaFoam does not work you may have some bigger issues with the exhaust valve. Could be a sticky lifter or a bad valve. Also you should have no more than 20 psi difference from one cylinder to any of the others. If you do you will have a rough idle and various other performance issues.