My 2001 s40 1.9 idles around 580. I have a check engine light that says misfire on 1 and 4. The coils and plugs were replaced about 5k miles ago. The idling problem started a little after i fitted a cone filter, and a sub and amp install hasn't really helped. Could anyone shed some light on this? Compression problem? Intake do it? Need new battery?

 

Also, what are any of your s40's idling at?