Our 2002 Ford F550 7.3 42k seems to have problems when towing heavier loads in mountains, it will be going right along and then you will loose all power for about 2-3 seconds, engine will almost stall and then continue to run again. You have to really stay off the the throttle to keep it from failing. The check engine light will turn on momentarily when it happens and sometimes it will turn on for a bit before the problem will happen. It never stays on long enough for me to go in and get the code checked however. I don't really want to take it to the dealer, but my local guy was pretty confused about problem he changed fuel filter and a few basic things but nothing has helped. Truck runs good rest of the time just under load towing hard it has an occasional freak out, trying to figure what it is! No fancy chips or anything truck is stock with 4x4 and 9' dump bed.