Idling issues with a 97 Honda Civic DX?

Ok so i have a 97 civic dx, d16y7 motor, and i'm having problems with my idling.
when the car sits in park it sounds like someone is hitting the gas and letting go and constantly does, when in drive there's no problem. I went to the pick n pull to get another IACV, but it does the same thing. I cleaned my old and new one and i've also cleaned the tb. The car still runs but this bugs me and i really want to be able to fix it. Any help would be appreciated.

Did we have a scan run for fault codes? Aside from faulty Idle speed control valve we may have a vacuum lean on intake side. Breathing issues?
if we can't locate fault have main dealer check it out as they will be best placed to pinpoint the root cause and rectify.

Assuming its not the iacv you replaced already, your engine is getting air from somewhere it shouldn't. Listen closely with it running and the hood up for hissing sounds of air leaking from a vacuum hose. Also take a can of something like carb cleaner and spray around the intake manifold ends and listen for a change in idle. Find the air leak you will usually solve the idle problem. Also if the check engine light is on don't ignore it, its your friend. Take it to Autozone or Advance Autoparts, or similar in your are, most of them will tell you why the check engine light is on for free. Thats good info to start finding the problem.