daver123,
First thing I changed on my car when I bought it was the spark plugs (Bosch Platinum 4) for almost no reason, worked great for almost 5K the I started getting misfires, rough idle I mean the whole shebang.
Everybody here told me the same thing AcDelco spark plugs, but I could not believe the spark plugs can go bad in 5K (especially such a fancy expensive ones). So I tried everything but the spark plugs, eventually ~10K the car was almost undrivable (literally). So in desperation I changed the spark plugs with AcDelco (as per everybody's advice), back to butter...70K later still butter. Now I still have a slight rough-ish idle (maybe is just in my head though) but definitely not the plugs, as I mentioned once, I remember waiting on a traffic light and some how I was annoyed by the vibrations caused by the intermittent ON/OFF of the wipers (that was above the idle) so maybe is just in my head (I had my 2 mechanics in the car and none felt any idle roughness but still I thing is something).
Hope yours will be better...