Yeh, don't sweat it, that's how it is. I recall back in 2007, I expected more power under those extreme demands but over the years I acclimated to it.
There is one thing you will want to check for with any E350 or E450, something that will rob power and it is a very easy mistake for a mechanic to reassemble incorrectly.
Make sure the large black flat engine air inlet piece is assembled over the radiator properly. It is the piece that the oval air inlet from the air filter snaps into. In taking out a bird from my a/c condenser, I had to remove that large piece, held in with 4 plastic push-pins. If the hidden hinged plastic part is placed incorrectly when installing it, air through the air filter to the engine's throttle body is severely restricted.
There was a recall around 2010 concerning that piece. Apparently a Ford line worker misunderstood it too. I can easily see that a mechanic could make the same mistake. I almost did it myself had I not previously known of the problem.
To check is extremely easy, takes all of about 5 seconds. Just grab the oval engine air inlet to the air filter, give a jerk upward to unsnap it and continue pivoting upward. Look in the hole it was snapped into. If you see a black plastic obstruction, you need to take that large piece out and swing the hinged plastic piece on the back side of it, the other way.
