I had the same kind of issue my vacuum was dropping on torque app by 2.0 roughly every 10 seconds ish... I had no end of the air cover piece the notorious piece that can fall off and stick in fans.. obv happened to previous owner anyway replaced that that seem to go away but idle would flutter from 730-790 could feel a pulse every 4/5 seconds...
Did 2 seafoam treatments one last week one yesterday aswell as was doing a massive service on the car as it has 38k on it but had no service history few receipts so did everything for piece of mind which was Plugs, Cambelt & Waterpump, PCV, DV, Cam follower, Oil change, Transmission change, Fuel filter, Full coolant change and fixed damn reversing light/parking sensors plug replaced brake light bulb driver side... transmission bracket and mount replaced and cleaned exhaust tips and quick clean under engine bay do that properly another day!
But yea the PCV and DV that was taken off looked fine but in my case I reckon it must of been 1 of them cause it idles really nice now they was both really old revisions as well maybe could of been a spark plug too I fitted Rev N PCV, Rev G DV and BKR7EIX spark plugs did notice old plugs were BKR8EIX.
Non ED30 mind but after all that purrs like it is new now :) just roll on next week clean up wheel hubs, new tyres, paint calipers and wheels :)