AC Problems

Is the pipe temperature the same at both ends of that tube?

You put less than 2 oz of oil. That should not be the problem. Was the condenser replaced before or after the last compressor replacement?
Did you add oil to the compressor itself? Where in the compressor?

One other thing if this has an expansion valve does it work? Is the piece that tells it to open/close making good contact with evaporator? And insulated or does it stick into coil and fell out or came out. Check that as well.

That plug is the crankcase and that is where all oil has to be added.

It sounds like your heater core is plugged up. Upon acceleration more pressure is going through the cooling system to make it hot. Have the system flushed and the heater core back flushed.

Lets clear the air about Jimmy's response. Jimmy apparently is not a mechanic otherwise he would know that you don't get air in the cooling system unless there is a leak. Posssibly a leaky intake or head gasket which is why pressure testing will not show anything. How often do you pressure test hot? Cold perhaps the gasket will not leak but hot it will. It is a sealed system. And also a 2006 impala will not have a 3.6L engine or a 3.9L. Those engines came out in the impala when the body style changed to the current style in 2007. It is normal for a heater core to be plugged after 4 or 5 years when the coolant is older. It is typical for a plugged core to give off more heat under acceleration as the pressure increases and decreases with lower rpm.
Jimmy, make sure you know what you are talking about before you tell someone that they shouldn't have their vehicle checked out by a professional. We can't see the vehicle in person so the best thing to do is guide not feed them BS.

Seepics for cooling fan diagram 2 pics

Please let us know what you find.

Cheers, Ken

Your compressor clutch could be going bad causing this like drawing to many amps. Or it could be low on freon. Or both. Have a pro check this out.