Symptoms of an aging fuel pump are increased bucking/hesitation when the fuel tank is below 1/4 level, and power loss at higher rpms (5000 and above).
How many volts do you measure across the battery when the car is running ? Should be above 13.5V. I had similar symptoms when the charging system was going bad and the voltage kept fluctuating, causing ignition and/or fuel supply problems under load.
Tiv
