206gti missing on one or two cylinders- already replaced plugs and coil pack. Suggestions?

Head gasket ??

Mother had issues with hers and extremely low mileage, replaced with another engine as the head was stuffed and it's just cheaper to not even bother looking once you know it's blown to replace the engine with another known unit
 
The miss is regular on one or two cylinders, so I'm assuming that it's the same one(s)... car hasn't been overheating so I'm assuming not a head gasket.

Don't have a code reader. Will get one tomorrow and see what it says. Thanks to both of you for your help!
Doesn't need to overheat
 
Top