How old is your fuel filter? How old is your O2 sensor? I believe 50,000 miles means time to change it. Does your check engine light come on at all? I went through the dying fuel pump issue a while back and had a rev limiter issue. I didn't get it to those revs very often. You may want to check your cap and rotor and the quality of the spark. If you get an air constriction of some sort it can act like that. At idle, you can pull the dipstick up an inch or so and see if there's a difference. You may have multiple issues and need new o rings on the dipstick plus something else. How often do you adjust your valves?