Definitely check codes. I know that some F250s don't have a boost gauge but if your truck does, I would encourage you to look at that gauge during acceleration. If it doesn't move, then the assessment of stuck vanes is accurate. You may have an older strategy too and if you don't drive this truck hard often then sticking vanes is a common side-effect. An updated strategy varies the vane angle during idle to avoid the seizing that accompanies infrequent turbo demand. Be aware that if you don't demand turbo performance then the strategy update makes sense BUT the updated strategy will also result in lower power and increase fuel consumption as well - a small price for the improved performance of the turbo in terms of compromise - OR you could take the truck out for a great drive every week and make sure to place some demand on that turbo.
Another thing causing under-boost other than stuck turbo vanes is a ruptured CAC boot. The loss of pressure during boost demand would provide less power than anticipated...likely accompanied by black smoke out the tailpipe too.
Check those codes. A good digital OBDII tool is a WISE investment as your warranty is about to expire (really should be a part of pre-warranty expiration for all 6.0L owners too). You really need to monitor several temperatures and pressures on a regular basis to avoid small problems turning into big problems.
An OBDII tool such as the Edge Insight CS or CTS or SCT TSX or ScanGauge II, etc. provide the ability to monitor these temperatures and pressures that the engine CPU reads but that the Ford dashboard doesn't display at all or doesn't display with accuracy or precision.
Critical values:
Engine Oil Temperature (EOT) and Engine Coolant Temperature (ECT). These values provide indirect measurement of the efficiency of the oil cooler (a stacked plate, liquid-to-liquid cooler) that has a tendency to block on the coolant side resulting in failed exhaust gas recirculation (EGR) coolers and then blow out headgaskets. The stock ECT gauge isn't linear and has no numbers; just a "C" and "H," while there is no EOT gauge at all. The ECT and EOT should never exceed 15 degrees Fahrenheit in difference after the engine is at operating temperature (about 190-200 degrees F for ECT). A bonus is that you can identify when the thermostat is failing too.
Transmission Fluid Temperature (TFT) is a great way of knowing how hard the transmission is working especially if towing. The TFT gauge is just like the ECT gauge; inadequate.
There is no Fuel Pressure (FP) gauge or even a sender and low FP will kill injectors...you'll have to buy an aftermarket sensor but some of the new OBDII tools will accept the signal input so you won't require an additional analog gauge.
The Exhaust Gas Temperature (EGT) is a partner to the TFT for towing to be certain, but monitoring EGT may help turbo induced seizure as well. Avoiding hot shut down prevents coking on the turboshaft. The turboshaft spins at tens of thousands of RPMs and gets HOT. A very thin layer of oil provides cooling and lubrication which is immediately denied upon engine shut down. If the turboshaft is hot enough it will cook that oil into sludge and your turbo won't work anymore even after restoring the unison ring (see here:
Diesel Technician Society). The ability to monitor EGT also requires an additional sensor just like the FP but several OBDII tools allow for the signal to interface so no additional analog gauge may be necessary.
The Edge Insight is about $400 as I recall and then some of the accessories will push the value upwards a bit. Nevertheless as your warranty expires knowing these figures and the ability to pull diagnostic trouble codes (DTCs) is a way to pinpoint problems early for corrective action rather than costly diagnostics.
Good luck - definitely make use of your extended warranty while it is available but invest in the digital gauge set to provide an "extra" extended peace-of-mind for when the warranty had gone the way of the dinosaur.
Jonathan
