'05 765 3900 hours, pulling a ripper, sometimes it won't pull past 88% load and there is power loss but no smoke. Out of the blue after turning around it pulls normal again. I stopped and idled 5 minutes today to take a phone call and it did it gain and ran this way for two hours before running normal. It never acts up while pulling, only after idleing or being shut off. I run in the constant engine speed mode at 1930 rpm but even after disabling that and trying to run wide open, it never goes past 88% load. Fuel filters were changed 30 hours ago. There are no codes or anything. This has happend briefly a couple times in the past but always corrected itself before I could look around too much. Any ideas?