A bit of a long winded post. Guys I am having issues with my 4bbl carburetor that I installed last winter. I have a 272 that is 30 thou over and the late ford replacement heads so compression is on the lower end along with a stock cam. I put a 57 B type intake on the engine this last spring and have fought with it ever since. 
So the carburetor is a 390 cfm 4160 that was 2nd hand and I rebuilt it. The rebuild included new throttle shaft bushings to make sure it was good and tight.
I have put on the quick change vacuum housing and have tried every spring tension. I have changed the vacuum housing from the 390 cfm without the check ball to one from a 600 cfm carb with the check ball to see if it helps and tried all springs. I have tried all pump cams and even put on a 50cc housing and tried all the cams including the brown and yellow ones. I have tried squirters all the way from stock which is 24 I believe up to 40.
I have made sure the arm is set so it squirts as soon as you get movement as there is not any slack. I have verified the float levels and have even tried raising and lowering them above recommended settings. I checked vacuum advance and distributor advance and timing is at 10 degrees initial. Vacuum at idle is 19" at 3000' in park and 15-16 in gear, it is a FOM, idle speed is 650 out of gear and 500 in gear. During my trials I discovered my fuel pump was weak so I changed it and it starts perfectly now, but I still have an issue.
The issue is that when I do anything other than a creeping acceleration I get a bog that can stall the motor AFM shows lean and it always lets me know when the secondary's kick in when cruising and give it more gas. If I step on it it seems to go fine. Is there any ideas you guys have? I am wondering if the carburetor is too small and the secondary's are coming in too quick? I am at my wits end and want to figure this out over the winter.

You may have a problem in the metering block (emulsion tubes), it's easier to try a different metering block than to repair it, however there are 2 small pressed in cups that have to be removed, drill a small hole in them insert a metal screw (not to far) and pull it out, you then can see inside and try cleaning, when done solder the hole in the cup and press it back in.