1979 Cutlass running rough

HELP
I have a 79 Cutlass, I just replaced the wires with new wires.. and the plugs, cap, rotor with used pieces. I also just rebuilt my Carb.
Idles, starts and accelerates great.... heres the problem.
Any time you are just cruising... without any accel at all.. it has a repeated misfire.. like a hiccup. it seems fairly persistant. a second or two apart. i had a burnt cam on my last car that backfired out the carb when i floored it . I am sure its not that when I floor it it moves damn good without hesitation... I think there is a light leak around the throttle shaft bushing on the carb, but was told it may or may not affect it. Any info on any other possibilities would be great. or any way of checking these problems with ease.
I'll try new Delco or Vgroove plugs first.. Thanks
Bill

Which motor & carburetor?

305/4bbl qjet

Does your QJet have the adjustment on how far down the primary metering rods would set in the jets? I have an '80 QJet with this feature which was for emissions adjustment but it also allowed me to nearly double my dads houseboat fuel milage.
There is a well with an adjustment screw in it right next to the well where the primary metering rods hanger is set on this carb and might be on your '79 too. If so, you can back the adjustment screw out a turn and give it a try as it will richen your cruise mixture to get rid of your lean condition.
Also, theres an aluminum plug just in front of the carb vent on the carb top on this particular QJet. Removing this plug gives you access to the primary metering rod bottom adjustment without taking the carb. apart every time.
check it out,
Chris