99% sure it'll be the throttle body that's gunked up
The idle on the 2.0 8v is controlled by a stepper motor on the Throttle Body, that cranks the butterfly valve open slightly to allow the engine to idle. Due to the crankcase breather going into the inlat pipe before the TB, all of the oily gunk collects on the butterfly valve and stops the stepper motor from opening it.
I picked up a 2.0 8v really cheap on ebay because it had this
problem, 30mins cleaning later and it was running as good as new