Seems like I have to keep advancing my timing

[chrismoore701]

I have a brand new 350 with a mild cam timing set at 12 degrees. . Ran great for 400 miles. Started to die and giving my all sorts of trouble. Played with the carb a couple times. Distributer was tight. Finally adjusted timing to 12 degrees and she ran great for another 400 miles. Then started to die again. Then started to stutter while driving. Trying to adjust timing again. Seems like sweet spot is around 20-22. I removed the vacuum advance which makes no difference in the rpms. The advance is connected to the top port on the front of my holly. Any thoughts? Brand new destributer