Hard to say how much but I think you would notice. I owned one of these and used it on a 1956 235. I didn't like it that much and then left it in a box in the attic, forgot about it and years later tried it on the 1959 235. I didn't like it that much on the 1956 but I'd be hesitant to say if it was because it ran richer. After removing it I used a Rochester BC for a few years and that one ran very rich. This by the way was around 1974 and up to around 1983.
The 3211s is leaner than the 2100s and the 967s is richer than either of those plus the idle jet in the 967s is pretty good size. So there's that, but it the price is right it could be interesting.
