2 things i have know to cause poor drivability hear and there.
1 a sticking float. i got one going on in my ram now and had this problem with a 2bbl chevy i had. when you mash it or have to give it a but load of gas for a short period of time the float drops open then when you let off the pedel the float don't come back up. this will cause you idel to drop from 800-900 to a blazing 500-200 and die. (ya i need to take a look at my bbd) up till then it runs like a good running slant with 143000+ miles on it.

#2 thingy is water in you cap. You didn't wash off the engine anytime in the past did you. go for new wires(manciniracing.com had them cheap) and a napa cap and rotor.(i use napa because of the brass connections) even if this don't solve you problem it is a good idea...

One more thing i thought of, Hows your coil. this would have the most direct effect on your spark. pick up your self a good hot coil. I like the MSD blasters you can get them from your local speed shop for around $30.
Good luck!
Frank