Well, I've reset the computer and low and behold the surging idle has disappeared. Let's see if and when it comes back.
D

 

you might consider taking off the air cleaner and inspecting the two plastic fittings that connect the hoses to MAF boot, they can crack and let in extra air. A small inspection mirror and drop liht should be all you need to see these parts.
Also check the screw clamps on the boot make sure they can be tightened from the outside of the intake housing.
Disconnecting the rear knock sensor is usually necessary to get to the top clamp as well as removing the fuel rail cover