How wide is the hole on the throttle body on the accord? If it is 3 inches, can a 2.5 inch steel tube be modified with a connecter of some sort to fit onto the 3 inch hole?

 

its 2.5 that why on the CAI kits they give you a rubber connector

 

the rubber hose, connector will do the job.
there's couple of popular diameter..

3inch, 2.5, 2.75 and yeah freaking four inch(aem v2, part of it is 4 inch.)

 

Wouldn't a 4 inch be bad for air flow??

 

great for air flow, bad for air velocity

 

damn it..jweller always steal my post! jk
to jweller

anyway..it make the air flow slower..
but aem v2 some how make it work..from the pic
in the aem v2 ad, appears that it's not all 4inch diameter.
the both end looks like a 3" or smaller..
it claim to beat the aem1..