Wouldn't think you are going into limp mode, as the CRD are very tolerant of higher boost levels.
Disconnect the battery and clean the MAF sensor just left of the Air cleaner, re-install when dry.
Check all your vacuum lines for splits or just brittle. Do you have any blowing smoke issues.
might want to change your fuel filter if its been a while.
Maybe its time to fit your gauges to monitor engine function, one less thing