if you're stuck with the auto i wouldnt do anything extreme, you might want to look into headers and a cold air instake system from aem.... but then again you might just want to go for the normal ecu upgrade rather than any physical mods at all (which is what i would do for an auto, due to it's control of the tranny)

the ecu upgrade can increase up to like 25% with a stock honda, so i'd say do that, not to mention you can do it in like 5 minutes

i must stess tho that if you plan to upgrade the ecu that you must see a mechanic or professional to adjust the ecu settings or you could mess up your car.... but it's still all good.