So, my 94 Bravada is having a hard time keeping heat moving.

It seems that when I let off the gas, either at a stop light, or just to coast, the heat in my Bravada turns cold. Apply the gas to just over 1000 rpm, and the heat comes back through the vents, let off the gas, goes cold again.

Any suggestions?

Already replaced the heater core, thermostat and radiator.

 

hows the coolant level? maybe time for a water pump maybe flush the heater core

 

Your either low on coolant, got a bad water pump, a blockage in the cooling system, or could be related to a vacuum leak.

Some of the blend doors are controlled by vacuum, some by cable. If you lose vacuum when you step on the brake, it could change where or at what temp the air blows out. I think on first gens the blend door is cable controlled ... and if so you can rule that out, unless it's coming out the wrong vents.