[71 super]

Check for vac leak around intake, the first has good color , but second looks to be lean. If deiseling idle def. too high. Remove mixture screws and spray carb cleaner through the holes. If the bleeds are clogged this will clean them out and may improve signal. Did motor back fire through carb? Check while running and see if boosters are dripping, doubt this is happening based on color of plugs, sounds like vac. Leak of some form. are you pulling from constant vac port or timed port? What type of dist. Are you running? If you have a dial back light with tach bring rpm to 3000 and see what timing is totaling out at. With that motor total timing should be in by 3000, set it at 32-36 degrees all in by 3000 and see how it does. No vac advance hooked up. The curve in dist. May be too slow for engine. Do you have vortec type heads?