When you say it will shut off at stoplights, is this only after it's warmed up?
First thing you want to do is make sure you've got the base idle set correctly. In a nutshell, you want to make sure the car is warmed up to operating temperature, then there are (2) connector pins you need to ground out to lock the IAC to center (hit up the search or VFAQ for details), before adjusting the BISS to the proper target.
If things still act up, it could mean your IAC is shot, which is not uncommon on the 4G63. Another, less common possibility is that your TPS has dementia. I had similar symptoms recently, and the logs showed TPS reading WOT at idle, which caused all sorts of fueling issues, resulting in the car dying once it warmed up.
Make sure you've got your idle/IAC set right before you start spending money on spare parts.
Good luck.