Why does my car Idle for so long?

it geting hella annoying that my car idles for such a long time, it sounds horrible? im still working on this Naturally Aspirated h23a1 Prelude and some of the work thats been done is AEM cold air intake, DC sport headers, magnaflow Catalytic convertor, and Cat-back exhaust system. ive even changed the o2 sensor if that had anything to do with it? I'm still planing to add a new throttle body an intake manifold and venom fuel injectors and to top it off i want to get new dual cam sprockets and fix the timing. will this fix the idle problem or make it worse?