Paul please see prior post:
http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=56177
I posted the same problem prior to you. I last thought it was an ECU idle mixture problem but now don't think so because the same problem you have keeps recurring. Lights or heater blower motor on and engine runs bad as if TPS is malfunctioning. Based on all the replies and parts replaced by others and yourself, I am certain it isn't the alternator/voltage regulator/dist./points/plugs/etc. I haven't been able to follow up on all the advice yet about shorts, bad grounds, corroded contacts...but I think that will end up solving the problem. The first one of us that has the time to follow all the advice given should hopefully solve the mystery "cold weather/electrical load" engine misfiring problem.