Mostly one or more sensor went off or vacuum leaking.
(Oxygen sensor, idle speed sensor, throttle position
sensor, intake temperature sensor, coolant sensor).
If you have later model car, you also need check knock
sensor. I think you must have a Japs car or German Car.
Right?
Go to dealer, ask them use VAG or Computer to read your
error code to figure out. The error codes are stored
in ECU when engine checking light on.
By my experience, one or two of wires which connecting
the sensors are loose.
I will exlude these parts: spark plug,gas filter,air filter
becuase you just change. But I think you still need as technician
to regap the spark plug if they didn't doing so.
I think your problem coming from dirty or unburned deposit on
intake, valve and dirty injectors. You need go to dealer to do
a complete tune-up, which usually charge above parts, clean
those I mentioned and re-timing the fire.