most likely ignition coils, or spark plugs. but sounds more like ignition coils... just not providing the spark when needed quickly/repetatively (i.e. under high RPM's)
fuel pump may be dying, if it can't provide fuel quick enough this can happen... but it doesn't make sense for this problem to stop when the engine has warmed up.
o2 sensor can cause similar symptoms, though you'd notice high idiling, same with intake problems (i.e. clogged air filter.)