Sounds like you may be hitting the PUMP LIMIT.
What is your Pump PW at full throttle? Compare that value to the PUMP LIMIT parameter.
The recommended procedure is to set PUMP LIMIT to 1020 (no limit), run the engine to full throttle and note the Pump PW. Then set PUMP LIMIT to 10 - 20% higher than what the pump runs at full throttle.
Joe