I think I might have an engine problem... :(
I agree with AJ about possibly needing more timing. When I first bought my car and got it running, the Vcan was connected to ported vacuum and the car didn't run well at start-up (no choke). Even after warm-up, the idle had to be set up over 800-900 just to keep running. When starting, even in warm weather, you had to feather the heck out of the throttle to keep it running until the engine got over 150F or it just wouldn't idle.
Mine had a Demon DP with mech. secondaries on it, that I think is a Speed Demon. It has the choke horn, (no choke flap mounted) so it's either a Road Demon or Speed Demon). It's running good, so I haven't dug into it to identify it.
Anyways,.... First thing I did was hook up a vacuum gauge and adjust the idle mixture screws to find max vacuum. That allowed me to lower the idle adjustment (closing the butterflies) back closer to where they should be. It helped but still wasn't quite right. I gave it a couple more degrees of timing (which helped) then moved Vcan hose from ported to manifold vacuum port.
The extra advance from that made all the difference in the world. Don't get me wrong, it's still a bit rough without a choke at initial startup, but smooths out much sooner and is much more drivable. It will idle at around 650 - 700 now and I no longer smell the heavy gas smell I was smelling when I first got it.
Like AJ said,... make sure you have enough vacuum to ensure the power valve isn't dumping and see if connecting the vacuum advance to manifold vacuum helps...... After you change your oil that is! :p