Both the old 4-Jet (square-bore) and newer 4-M (spread-bore) are referred to as "quadrajet" in original Rochester literature.
"Standard" jetting is sea level to 4000 feet with no changes.
Rebuilding to ethanol specs should only mean a leather accelerator pump instead of modern man-made material, and possibly, a few misinformed individuals will use the old monel steel needles instead of the "rubber" tipped needles. Ethanol will cause the monel steel to rust.
Did the issue occur PRIOR to the carburetor rebuild?
If yes, maybe need to look elsewhere.
If no, maybe take the carb apart and check float settings.
Sounds to me like you are having choke issues, as you state it smooths out after warming up, but think about the timing of the issue (when it started).
Jon
