Due to bad gasoline on the highway the spark plugs are worn. There was an evacuation of the car and then it got to the mechanic. Old spark plugs (iridium) were replaced with new (iridium too), after which the engine worked for some time on the cleaning fluid instead of gasoline (mechanic turned off the suction from the gas tank). After that the throttle has been cleared and the battery terminal was reset.
Then significant engine rotations surges immediately began, especially in idle state. There was an idea that it's something about the throttle adaptation, but I've already ridden more than 5 thousand kilometers. Maybe the problem is in idle air control actuator? Any advice and explanation would be appreciated.
P.S. The mileage of the car is about 150000 km. Errors are not displayed.
P.P.S Immediately after starting the engine and some time after that, the engine works quite loudly (there is "murmuring" noise on Parking, Shift, Reverse, not on Neutral). If immediately after starting the engine to switch to the Reverse, the murmuring noise becomes scary loud.