Yes, more info is needed.
How old is your fuel filter? Change it first.
The next thing I'd look at is the air box, filter, and all associated tubing for restrictions like a mouse nest.
Look at the turbo while the tubing is off. A bit of side-to-side shaft movement is normal, just make sure the wheel doesn't contact the housing. There should be NO in-and-out shaft play.
Check your Fuel Shutoff Solenoid. Make sure the boot isn't coming apart and binding plunger travel. If the boot is disintegrating, pull it all off and make sure none of it is inside the spring. The boot isn't necessary unless you're in the rust belt. Make sure the plunger is making full travel.
All that checks out, take your fuel cap off and pull the 5th wheel and see if there's a difference. If there is, your tank vent is clogged.
Was there lots of black smoke when he couldn't get up to speed?