Classic/Antique Car Repair: Idle on a 69 Chevy Impala, vacuum hoses, 69 chevy

Question
I just bought a 69 Impala...first thing I did was a tune-up...change sparkplugs, wires, distributor cap, rotor, oil and filter. It came with a Rochester Quadro-jet carb on it that wasn't working properly, I bought a Holley 4-barrel carb and put it on instead..Oh, the engine is a 327 by the way. Now, I have the idle set pretty good when it is in park, however when I come to a stop and it is in gear it wants to stall. I can't figure out why. Is there something else that I haven't done? I changed all of the vacuum hoses that connect to the carb and have adjusted the carb a half dozen times as well as the distrubitor. Please help me.
Thanks

Answer
ok sounds like you  did all right did you put all vacume lines in proper places, or plug any if need be also is the carb large enough for the car/ h.p. ? it sounds like a adj. or a vacume problum. look again at that also is the ilde high enough - is there a p.c.v.valve hole in back ? it might be a simple thing so dont over look any small things, hope i could help you