I found these charts presumably from Weber comparing their carb performance versus the stock Carter. Obviously theirs perform better than the Carter (upper lines for 32/36 and 38 - I can’t tell which is which) in all cases but what is telling (no big surprise here) is that:
1) the 258 gets max torque at 2K and tanks after 2.5K;
2) the 258 gets max HP at 3K (3.5K Weber) and tanks thereafter;
3) most economical operating range is 2K to 2.5K.
No really new info here, just nice to finally see some charts …