Coil pack - ignition coils.
Vaccum leak. There are different ways. Easiest is a start pilot spray. If you spray it on a leak in the intake area in general the rpms of the engine raise.
Be careful and don't spray starter spray on hot engine parts.
There might be other leaks. So one additional check could be to open the oil cap when the engine is on idle. If the ilde gets rougher and again gets smooth if you put the oil cap again on, than evereything seems to be OK at first sight. Also the throttle response should be worse with the oil cap off.
If the idle doesn't change / doesn't get rough this wlll be a sign of a vacuum leak.
At a workshop you can do a professional vaccum leak test. By doing this you can test the complete engine.
Regards
Markus
Regards
Markus