I'm unsure of your rotor setup but just to let you know that extended bars were not standard until 2001. Also just two reverse bars can take a lot of power away not to mention what four or six can do. We used to dyno all combines before we extended bars and usually found them to be very close. Not to say that pumps could not be set to perform better. Number one thing I have found for either Deutz V8s or Cummins C-series with low power is the charge pump. We have found junk in check valves at charge pump on both them engine set ups and found bad seals in the C-series charge pumps. We have found that machines with discharge beater instead of chopper need the serrated blades out in the heavy straw conditions. If beater does not such straw from rotor it will gobble up lots of power.