2009 Sierra 5.3l, extended cab, high idle

[SeaDonkey45]

Took my truck to the dealership because it was having issues of when you come up to a stop sign or traffic light, wanting to keep going, it didnt like to go below 1500 or 2000 rpms. If you take it out of gear, it will momentarily idle up to 2500 and then come back down to normal, THEY said oh yea thats common, probably the throttle body carboned up, we charge 125 bucks to clean that. I said my truck is still in warranty, what the hell? I received no explanation other than that aint covered, I said its an under warranty truck that doesn't run or drive right, how is that requiring a charged fee? Anyway, long story short, I have worked on my own cars for over 25 years, So I took off the MAF and the throttle body and cleaned them both, and yes the throttle body was extremely gunked up, I used only MAF cleaner on that and I used throttle body cleaner on it. I had the battery disconnected the entire time as well. Reassembled and drove truck and it drove just fine it seemed until i pulled back in my driveway, now it will idle up to 3000 or more rpms, and just stay there. I took it back out for another drive and after a few miles it seems to be running fine, UNTIL you come to a stop sign, it doesnt want to stop, and if you take it out of gear, will idle up to 2500-3000 rpms again. Pulled back in the driveway and ran a scan on it, and it reports a B2AA code, I cannot find any such code anywhere, any ideas people? I know the maf is clean and the tb is spotless, I took the cover off and make sure I plugged in the breather tube,etc.

[SeaDonkey45]

Oh sorry, left out some stuff, the truck has 41K miles on it, has no tune jobs or anything else done to it other than a magnaflow catback system and a k&n filter, both of which have been in/on the truck for years. It does have the afm engine, in case that matters.

[SeaDonkey45]

anyone?