Diesel: Intermittant reduced power

[Racerhoze]

So my dad's 2009 X5 diesel has 56,000 miles on it, and it has now twice thrown a code and began operation under reduced power. Both times the warning went away after a restart. Both times the code was thrown at highway speed during a heavy throttle application. The code was scanned at the dealer once already and it read something like "charge air pressure unexpectedly low" or something like that. Basically a boost leak situation. Has anyone else encountered an issue like this or have any suggestions for troubleshooting?