This one is tough to describe. Under full throttle my 92 300E (3.0 engine) seems to lose power in the last half of acceleration before shifting up to the next gear. This is true in passing gear as well. If I back off of the throttle I can get most of the power back. Spark plugs and air filter are new and there is no engine miss. Could it be a fuel filter? Fuel pump? The Fuel pump is very quiet. Any help is appreciated.