Car's been doing just fine for the past few weeks but today I went to work and noticed some shaking when standing still at a stop light and looked at the tach and saw like 450-500RPM idle with the A/C off. A/C on gives it 700-750 maybe and it's better but.. It hasn't stalled yet but got very very close a few times. It driver fine and cold idle was fine as well when I drove off this morning. I haven't really done any diagnosis yet but I will in my break. Any ideas what to look for? Engine is stock internals with a 4-2-1 stainless manifold, 2.25" exhaust, 200 cell SK Import cat, stock O2's. I replaced the intake box from the rubber hose down to a pipe with a open K&N style filter. I did just put a few new speakers in the doors and a 560w sub + amp in the trunk (it's a sedan) and I did have the radio playing. I also put new headlights (angel eyes + H1-H1 conversion) and new JDM style clear tails in it as well as clear black side markers. Also replaced the speedo bulbs with SMD T5 LED's (with built-in resistors). Maybe it's alternator related? I have my OBD2 scanner with me so I'll double check idle speed with OBD as well if this ECU sends that kind of data over OBD.

EDIT: Shame, no normal ODB2 port on this model. Need to get a 3 pin Honda to OBD2 plug first. Alternator is fine, 14.24v idle charging.

Here's what it runs idle standing still in neutral (manual).