installed new battery-now idles at 1,200 rpms

I have a 99 with the 3.5 liter engine. I recently put in a new battery before the cold weather starts in MN. My old battery was almost 4 years old. After the new battery was installed the engine now idles at about 1,200rpms even after the engine is at normal operating temperature. Does having the battery disconnected when the new battery was installed mess up the computer?? or could it be something else?

It shouldn't (although you never know with this car...). Sounds like the alternator is putting a load on the engine. Perhaps the battery isn't fully charged yet, or maybe there's something wrong with it, like a dead cell...

I solved the problem. I move the low idle set screw 1/2 turn back to lower the rpms, but then made the gas peddle stick when starting to accelerate. I inspected the throttle body plate and it was covered with varnish and gunk especially the back side. I used a tooth brush and 1/2 can of throttle body fuel injection cleaner to clean it up. I did it 2 separate times. The gas peddle is now stick free and the idle screw turn back to the original position and the slow idle is back to 7-800 rpms.