Cold Idle Surge Help 78 320i

[slvreagl]

I'm new to this board, just purchased a 1978 BMW 320i for the second time in my life, I cant help it I like 'em.... Anyways, its got 178,000 miles and runs great when warm.. I had to replace the Billion dollar thermostat, and recently put new plugs in it.. My problem is in the morning when I first start the vehicle, its a little hard to start, and after its started, the idle surges from 200 - 1500 rpm untill it finally dies, after it reaches the first line on the temp guage it runs idles and drives perfectly, I also noticed the gas mileage seems to be a bit low, the old plugs looked average no idea how many miles on them since last replaced. I have a standard haynes (crap) manual but cant find a dirrect solution.. I should mention that there is a vacuum line going to the intake plentum (second fitting from the firewall) that is disconnected, if I plug this line when cold the engine will die, havnt figured out where it goes yet, or what its full function is.

ANY help would be great appreciated.... slvreagl001@yahoo.com