When you replaced all 4 Ignition Coils
, you should also have replaced all 4 Spark Plugs at the same time.
Use the NGK Part Finder website to get the right plugs.
You want the "NGK BKR6EZ"
I also used to have a 1.8 Lag II. You also want to consider changing the air filter if you have not done so already. Its only 3" by 4" and blocks up in just 1 year.
Its only a 10 quid item and greatly improve fuel consumption if the existing one is dirty / blocked.