I've been having a problem with a stumble and sometimes cough through the carb / throttle body under light acceleration. I had an old style Holley EFI (projection) system which I thought was the problem. I swapped it for an Edelbrock 1406 (600 CFM) carb, and I still see the same problem. I installed an air / fuel gauge and it's showing a very lean condition during the light acceleration, it goes back to a normal condition if I tap the throttle or let off. I'm thinking maybe a vaccum leak in the intake, or something's up with the timing not advancing. Any help would be greatly appreciated!

Here are the details:
82 z/28
mild 350 with Edelbrock Performer intake, and Edelbrock carb
Mallory Unilite distributor with a pro-master coil (both coil and module recently replaced)
700R4 tranny - stock converter (normal stall speed)

 

i would check the bottom of the carb for vaccum leak first.I c u just replaced the mod and coil did u use the mallory resistor between the batt and the distributor ur supposed have a ballasist resistor or u will burn the mod and coil and also dont forget to cut ur switch off cause those unilites will burn up easily I did this once I dont know if u needed this info thought id throw it out. BUt check the base of the carb first for leak.

 

I had a plate for a NOS set up that I thought may have been causing the problem. I removed it and placed the carb directly on the manifold with a new gasket and lots of sealer. I was thinking it could be the same thing. That's why I'm now thinking I might have a leak somewhere between the manifold and the heads.
Yep... I do have the ballast resistor before the coil.