0.18.3 corrected an issue where a previous change to the flow system (back in 0.17) prevented pumps from achieving >6,000/s flow rates. The fix was to change fluid_box height from 2 to 4. This change should also be applied to Bob's so that it matches the base game, allowing Bob's Logistics pumps to reach their maximum pumping speed.
Reference: https://forums.factorio.com/80585
