Ghost - a few thoughts:
(1) Jerry (Hot Rod Lincoln) and panic have both alluded to issues with dual carbs on a 6 cylinder Chevy engine. This is due to the fact that the Stovebolt six has 3 sets of siamesed intake ports. With two carbs, the carbs interfere with each other in trying to feed the center 2 cylinders.
(2) Joe mentioned the Carter W-1 is an excellent choice if you must use 2, and panic mentioned that with a common plenum, the 2 carbs should be smaller than 1 (original). The W-1 is an excellent choice, as the W-1 has a mechanical power system (the YF power system is vacuum). With a vacuum power system, the vacuum springs SHOULD BE NEW, and the compression on all cylinders very close to identical.
(3) Joe also mentioned that if one uses 2 carbs, they must be EXACTLY the same. Same identification number, same calibrations. (You did not specify which YF carbs you are trying to run).
(4) You mentioned quote: "There must be a more modern, reliable and smoother running carburetor out there, that I can buy and use as a pair." (Opinion) there is NO modern single barrel carburetor that is better, or more reliable to run in multiples than the Carter "W" series (the W-1 is an S.A.E. size 2, and the W-0 is an S.A.E. size 1). The YF is excellent in a single carb environment.
(5) (no offense meant) your post requires us to guess. We don't know what carbs you are using, straight or progressive linkage, with or without chokes, and the calibrations. While (1) through (4) above should be considered "food for thought"; ASSUMING both of your carbs are EXACTLY the same, I would suggest interchanging the carbs to see if the issue follows the carb, or stays with the location!
(6) efi has been mentioned; I will make no comments on efi, other than I personally do not like it for a myriad of reasons.
Jon
