Think I have a missfire

I have never had a misfire before so am not really sure if I have one. Problem is I did lots of things at one time and am not sure if I now have a misfire.

I changed the sparks, exhaust, coilpack clips all at the same time. The car seems to almost have a knocking sound from the exhaust now, but sometimes its not there. I thought maybe one of the coil pack clips wasn't making a conneciton so I re-did them all, no better. I was thinking the coilpack insulation trick to see if there is a hairline crack in one of them and the spark is archingfrom the plug.

How do I tell if one of my coil packs is bust?

How do I tell which one is not firing correctly?

Is there anything else I can test or that springs to mind as the knocking? its not loud but I am not sure if its not just the sound of the new exhaust, but its not there all the time.

run the engine and pull off the electrical connectors to the coil packs one by one and listen for a change in the noise the engine is making. As soon as you pull one that doesnt make a difference, that will be the one thats not firing. Swap the coil pack over with another one to see if its that busted or not.

Good plan.

I was hoping someone would tell me that was ok and won't kill my engine

What plugs did you fit?

When is the missfire, at high boost?

I don't even know if it is a mssfire, it sounds like there is a knocking in in the engine noise coming from the exhaust. Its always there, tick over to high boost, but sometimes it is not there at all and the engine sounds smoother.

Iridium IK22 plugs

If you changed the exhaust and you now have a knocking from teh exhaust, is it not more likely you haven't hung the new exhaust correctly?