95 Lumina Heater

First when it's cold it doesn't get very warm no matter how long you let it run. 2. the air doesn'y blow very hard even at four and when you are coasting the air comes through the dash vents but when you press on the gas the air doesn't flow through the vents until you are coasting again. when you press on the gas the air goes from the dash vents to the floor vents un til you are not accelerating. It does the same thing when the ac is on. Does anybody have any clue of what's going on?

Vou have a broken vacuum line, a blocked and dirty core, and possibly a bad thermostat.

The vacuum line will make it come out the wrong position when you step on the gas, the dirty core will impede airflow, and the thermostat will keep it from getting warm enough. A radiator fan that runs contantly will do that too...