Fired up my freshened up 496 and ever since has a stumble hot. Plugs are light gray in color, I use VP 110. Idles smooth at 1200 RPM, but has stumble right of idle. Carb is a 4150 1000 cfm Pro-systems carb. Tried richer on mixture screws, still the same problem. Timing at 34 degrees. I did change the cam to 274/280 from a 268/272 flat tappet.

Primary Main 84
hi air 32
idle air 76
idle feed 35
PV 6.5

Thanks Matt