First thing to check is tire air pressure. My 250 tire sticker on door jam states 75 front 80 rear. Mine steers best, when towing, at this psi. When tires/truck was new, it steered best at this pressure, even when not towing. After getting some miles on tires (maybe 5K) the steering noticeably improved. I still air to 75F 80R when towing, but lower rear to 70 psi when not towing. I should mention, my truck has HD service suspension (similar to 350).
You are removing very little weight from the front axle with that pin wt. Not sure how many miles on your new truck, but I'd give it a little time.
Jerry