Hi all.

My car is a '97 fiesta mk4 1.25 and its had a minor misfire for a while now.
It goes through the rev range fine, and I have no problems, other than when the car is sat idling, it shakes / vibrates, and the engine doesn't purr, it was quite rough.
Yesterday, I did somethings to try and fix it, first changed the fuel filter, then cleaned the MAF with some brake cleaner, then sprayed a little in the idle control valve, then I did a compression test and replaced the spark plugs.

This made it 10 times better, it purrs almost perfectly, but it still has a very slight misfire, I can feel the engine vibrating very slightly, Like it has when I've had the misfire, and now I don't know what else to do.

I need to test for air leaks, but apart from that, what else can I do?
I read the coil pack and leads are a common thing that needs to replace?

Also, when ever I turn off the engine, from the exhaust, it sounds as though there is alot of air being pushed out, what could that be?

Cheers, Jason