Faulty Ford TPS
Some 2008-2010 Ford F-250 Super Duty trucks equipped with a 5.4L engine may exhibit a MIL on with DTC P2135. Drivability symptoms may include intermittent rough idle, idle speed below specification and/or reduced power.
The problem simply may be the TPS (throttle position sensor). Replace the sensor with P/N 6L2Z-9B989-D.