Mine every now and then (At least once during an entire trip) will, with very light throttle, just below 2,000 rpm in either 2nd or 3rd gear will start to get rather rough for about 5 seconds, almost like a highly cammed 4cyl just before it comes on cam. (Or a bridge port on a rotary engine)
After that, no problems.
I thought it was the DPF regeneration process (Retarding fuel timing, blocking the airflow off to the engine, opening the EGR valve to help increase exhaust gas temps to help burn off DP in the DPF)
Yet, as we all keep finding out, Australian i30's do not have a DPF, yet still meet the same Euro emission standards of EU i30's that have a DPF fitted.
Has Hyundai found a new way to meet emission standards without a DPF?
News to me.