Fast idle thermo valve maybe? Does it change it's idle once it warms up?

The idle surges between 1200 and 1300 are most likely the ECU adjusting ignition timing, there is a little fine idle control through that method and it's pretty common in modern ECUs. Does it drive and run ok under load? If you're having coolant temp sensor problems, or coolant level problems, those will generally have an effect when it's running also, not just idling. Just to be safe though, check the coolant temp sensor. Most of the other sensor problems (MAP, CAM, crank, etc) will affect running all of the time, and will often throw a code. Vacuum line problems can be subtle though, and hard to pinpoint.