I would be checking to see if the thermostat is opening all the way first... May as well just replace it, they're cheap. and easy to swap.
Secondly have a look to see if all the f*cking annoying little vacuum/anti pollution hoses are connected to something. If you see a loose hose, attempt to find where it goes. If you can't, just plug it with something and see if that makes a difference.
I would wager a tube has fallen off the cold start/idle enrichment system.
Also remove the intake from the manifold, visually inspect the throttle butterfly for corrosion around the edges, it may not be forming an adequate seal at idle. Its also possible the intake manifold itself is a little gunked up, spray a bit of carby cleaner in there with the engine at 2000rpm and watch the smokeshow :)
3300 is about right
The bonnet is specific to the seca... Hatch and sedan are different.
Seats from a csx, sx or RV variant are slightly better, and bolt straight in... Still nothing special though.