Help!!! Chevy 350 has a dead spot
 

I recently picked up a 72 nova with a 350with a Holley 600 cfm 4160. The car ran decent but would bog and want to die when placed in gear after checking the vacum I determined that the power valve was opening so i replaced it with a new 4.5 holley power valve, and now the car has a dead spot slightly off idle and breaks up at higher rpms. I changed the cap and rotor and put new plugs and wires on it and rebuilt the carb with no change. I'm stumped at this point any help would great.