Ok.. You could have a bad IAC motor, THis is very common!
Also, sounds silly, but if the transmission fluid level is low, then this can cause your stalling too. Be sure the transmission fluid level is correct, low fluid level can cause torque converter clutch
release problems. There is a TSB about this problem. It is TSB# XXXXX Verify the fluid level is normal, a low fluid level on this transmission can cause the torque converter clutch to disengage slowly. This transmission is very fussy with the fluid level and the level on the dipstick can vary greatly with transmission fluid temperature. Make sure the fluid level is Ok according to the transmission fluid temperature, see service information for the details.
Also, If you can get access to a scanner, Check the Clutch Volume Index (CVI) on all the clutch packs. On this transmission the normal values are as follows: L/R=45 to 134, 2C=25 to 85, O/D=30 to 100, 4C 30 to 85, U/D=30 to 100.
If all of that stuff checks out ok, you might just have a bad camshaft or crankshaft position sensor. These two are very common!