Lumpy idle

I've now over 3000 miles in on an engine just reached 80k. I did the head at 78500 and I'm experiencing no problems, other than a cheapy thermostat.



I've always had a lumpy idle. When I first start, sounds like a good k, but will then drop a bit onto 3 cylinders on/off before finally settling onto 4. It has NEVER misfired other than at start up from cold.



Listening to the engine today, it seems to cut out momentarily but still keeps a 4 cylinder tone.



Timing was all in line when it went back together. I've just changed the spark plugs.



I've had nothing alarming on my OBD reader and no warning lights on the dash. Pulls just as hard as my friends 1.4 ZR.



Any pointers?

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