EK9 Rails or if you searched (http://www.ozhonda.com/forum/showthread.php?176160-fitting-recaro-sr3s-to-ek-civic) bride RO rails which fit Recaro SR3s and, bride.
Should've gone for a full under body diffuser if you want to see a noticeable difference in grip/downforce/track times. Canards don't do that much in terms of angle of attack and their main purpose...
Agreed with the rest, don't look into throttle body unless you're planning to upgrade the fuel rail, pump, etc. But even then that would mean you're quite a way in your mods list.
In regards to installing headers, I believe (don't quote me on this) that they wont do much to a car's performance, unless you go and get it tuned then you will be using them for what they're worth....
Adding wings/diffusers/lips/splitters to your car will not make any difference to your car's performance, it most likely will just increase drag and hence will actually decrease the performance.
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Give us feedback as to how that goes because my Civic pings when going uphill 3rd gear at ~50kmph. And the only real way I found to stop it is to let off the throttle a bit