95 accent Mid range rpm problem

hello,
i have a '95 accent, manual, that has the following problem:
on cold days, it has a hard time starting (about half the time), once it stars, it runs fine, but when it warms up, it sometimes idles very rough, runs okay at low speeds, low rpms, runs okay at high rpms, but mid range it bogs down, sometimes feels like it's going to die.
I have changes the plugs, wires, MAF, and the purge valve, the O2 sensor is giving the right readings for voltage...
any ideas???
 
Oh yeah, i can sometimes here my fuel pump, when I am driving, is that normal?
 

hearing the fuel pump at idle or while driving is not normal. it's most likely that the pump is going bad. if you have access to a fuel pressure guage you can check what your fuel pressure is like when starting and start from there.