deffinately sounds like a sensor to me good luck

Thanks for the help, Cummins Guy and Lunk! I just got back from the diesel shop. The problem appears to be fixed! Steve hooked up his SnapOn graphing scanner and it showed the injection control pressure sensor (at the front top of the driver side head) was funky, particularly down at the lower RPM ranges. He had the local ford dealer bring us a new one, installed it, and then the scanner showed proper pressure variation at the lower RPM end of the scale. Looks like a good fix to me, and I also found out good info here. You can check this sensor easily by just unplugging it. The PCM will then default to a running value when unplugged, and will run good enough to get you home. Good to know! Thanks again, guy's! Dr. Phil