[ChevyTech]

You have the open and closed loop backwards.

The system is in open loop when started cold and does not go into closed loop until specific criteria (oxygen sensor hot enough, timer expired) are reached.

When running in open loop the system is very dependent on the coolant temperature sensor reading, TPS, and the MAP (Manifold absolute Pressure) to calculate the fuel needed to run well.

By what you described, the mixture is off. It may be running to rich when cold. Here are some things that can cause that.

IAC not increasing the engine speed enough- bad IAC, IAC connections, RPM reading (reference pulse error)
MAP reading low vacuum making the mixture rich.
You ruled out - to high of fuel pressure.
Injectors to big for the engine or leaking.

With a cold air intake, if it has no heated air intake, ice can form in the TBI up to 51 degrees. Above that it can't be the problem.

If you can post what you have data logged I would look it over. A log of a hot idle where it is running well will tell me the most.