People think that all of honda's shit is crap, and when they start "tunning" there stuff, they replace it with parts that actually have worse quality. True a dx air box is designed to do its purpase and be quiet instead of just being for letting air in. Yes, goind with CAI will help. However, Honda is one of the best engine designers in the world and alot of there stuff that has no diffrance in ride comfort, safety, reliablility, and emmissions they will put the best stuff in there engines. Stuff like bearings, and ignition systems, honda only goes with the best and you will have a tuff time finding better. Also with stuff like tranny fluid, the honda MTF is the best you can run in hondas because honda designed it to work best with there trannys
(sorry to go so far off subject but you know what i am saying)
there is a set of numbers on the side of the block for the main bearings, and letters on the crank. Match the two up and call the honda dealer, they will know what to do. There are numbers on the rods too.