I have a 1999 Intrepid that has an annoying problem. About a year ago, my car started running rough when I put it in reverse after it has been sitting overnight. It usually happens in the morning on on cool days. I crank it...runs fine...I put it in reverse and it starts knocking and I hear a sucking sound around the intake just above the EGR valve. If I put it back in Park, it revs up for a few seconds and back down. The episode lasts about 20 seconds. After that it runs fine. My check engine light also stays on (code P042, insufficient catalyst on bank 2). I was told by the dealer and my mechanic that I needed to replace my left catalytic conver, which I did. That did not solve the problem. I am starting to suspect a bad EGR valve or some kind of vacuum leak. Could these two problems be related? Any suggestions are appreciated.