Trouble

I would still re check the pump. I have had to replace fuel pumps that where only 3 weeks old! Make sure if the pump is the issue to buy a AC delco pump. Once and done! If your pump is not the issue have the ignition module checked (is mounted under the coil on the driver side cylinder head). Those when failing will work great when cool but as the electronics break down from the heat will give you the issue you are having with your car.

It does sound like it is running lean....when the choke is on the air fuel ratio will be higher on fuel....once the choke is off then you are lean. I would pull the mass air flow and clean it....while you are doing that look for broken, cracked, or missing vacumn lines...that would let more air into the mixture.