Biggest difference in a PowerStroke versus a Cummins is,,, THe Cummins come very tight from the factory, and get better with age, where they wil be still darn tight at 10,000 miles, and at 50,000 miles they will just about be running real good, and ready for the next 50,000 and at 100,000 they are real smooth, good power, and don't have any funny noises.
A PowerStroke runs real good off the lot, but at 25,000 miles starts to loosen up, and at 50,000 starts to get loosy goosy, and at 100,000 they seem a bit old, nevermind 100,000+, they get real loose, and aren't the same diesel they were driving off the lot.
Let 'er break in, you are probably just feeling the tightness of the motor. It is a straight 6, and is prone to some different vibes than the v-8 you are used to.
Merrick