That was my 1st thought too. IACV. I would try to remove it and clean it. My 93 Civic Si had 214,000 miles and idle rough too when I got her home from Michigan (to PA). The 1st thing everyone recommended was remove it and clean it with some carb cleaner. Also check the rubber seals and the screen. It was clogged pretty badly for me. I actually cleaned and rinsed that thing about 4-5 times. Made sure it was dry and then reinstalled and she idled perfectly for about 2 years until I needed to replace the FITV last year. LOL.