Q: I changed the spark plugs and now my car is puttering, revving up on its own, and making a whistling noise

If these symptoms did not exist prior to the spark plug replacement, it would appear as if something was disturbed, disconnected or broken during that maintenance. You want to make sure that all of the plugs were installed with the required gaskets and tightened to the correct torque, using only a torque wrench. if the plugs are loose or gaskets are missing, air will leak in and out of the combustion chambers. Also ensure that no engine sensor electrical connections or terminals were disturbed or left disconnected and that all coil on plug assemblies are intact and properly connected. If none of those checks resolves the issue, please free free to schedule a rough running engine diagnostic to identify the problem.