Dneff85

I'm not sure if I posted this in the right spot but here I go anyway. I have a 2002 Subaru Forrester Replaced o2 sensor about a year ago. No symptoms of a problem but the CEL light came on. Six months ago while driving it started losing power unless giving it half throttle Three months ago started hesitating and surging occasionally. CEL came on reading knock sensor. I replaced the knock sensor with cheap one from eBay Engine continues to surge and hesitate I replaced spark plugs and wires 1 month ago it stated back firing and shaking badly I haven't driven it much since then I took it into the super dealer and they couldn't find anything wrong with it. Connected to their diagnostics and told me nothing was showing up Last week I got a code for misfire on cylinder 1 and 2 I replaced the coil pack with a used one, but nothing changed. It misfires when engine is cold (it's winter now) and after letting it idle for at least 30 mins drives fine. Should I check other sensors? IAC? MAP? What is wrong with my subie? I'm so tired of this