Omgosh!! I'm so happy I found this thread. I've been tracking the rough idle for 2 years I swear. I have a lot of new parts through this process though, ha. 2004 Colorado with 139,000 miles.
Used seafoam as directed, let it sit about 10 mins, started up and some nice smoke rolled out, took a cruise till it stopped. Still rough idle, which I figured but glad I did the sea foam anyway. Put some in the gas tank because I guess that's good to do.
Took off the throttle body, man was it dirty. Cleaned it spotless, used a whole can of throttle body cleaner, most of it at the end just blasting it clean.
Got it all back together and about cried, rough idle was gone. Took a drive and the shutter I had on deceleration was also gone. Sat in the garage just watching the RPM needle not move at all. The real test will be after tomorrow when I change the oil and put some miles on.
Thanks for all the advice on this forum! Wish I had come across this thread a long time ago. Amazing!!!