EGR Valve replacement

I have a 1998 Accord EX V6. The check engine light came on a couple of weeks ago. ODBII said EGR valve insufficient flow. I replaced the EGR valve myself. A few days later the light came on again. Same ODBII problem. I called the Honda repair service and he said that I needed to get into the intake plenum and drill out a hole that had likely built up a blockage.

My experience with cars is light shade tree type stuff based on using a Haynes repair manual. Can anyone tell me where this intake plenum is and how to get to it? Do I need to take off the intake manifold to get to it? Thanks for any help that you can provide.

Thanks. This is just what I needed. I have 140K miles on it so it looks like it will come from my pocket. It looks like some work to do this weekend. Thanks again.