ok this is a weird one it runs completely normal when until you turn on the heat or ac and then it goes bad the van spudders and stalls and then if you turn it off it goes right back to running fine. If the heat is left on smoke develops under the hood it may be coming from a wire or something but it is difficult to see where. Winter is coming and it is my only car what should I do any idea what it will cost and should I take it in?

find where ya fan motor is...check the connection.mine had flimsy plastic connector.when it came loose, the plastic stated to burn and smoke..

Is your heater switch set on a defrost position? Is your A/C button in? Either of those will activate the A/C compressor. If either is the case, perhaps your A/C compressor is seized, putting a load on the engine. Could be the belt smoking.

It almost sounds like the plug to that resistor pack, the one that varies the fan motor speed. It's on the firewall, backside of the heater.

I vote compressor- why not unplug connector to keep it from running and see if the problem stops.