One thing that article didn't mention is an intake manifold gasket leak at cylendar 1. This is a common problem with our beloved VX.

By all means, first check your plug and swap the coil pack from cyl 1 to another cyl to see if the fault moves.

Spray PB Blaster around the intake manifold gasket (near cyl 1) with the engine running. If the idle changes, then indications are that you have an intake manifold gasket leak.