Clutch, Master Cylinder

I have a 95 Nissan 300zx with 165,000 miles. I have been experiencing a lag/loss of power between each of my shifts at low RPM almost like it is slipping. There is no power at low RPMs, but after it catches and revs past about 3k RPM it then feels normal. It appears that the play between the time the gear begins to engage and the time it actually catches is a pretty wide span of clutch pedal play, but I just recently replaced the clutch due to slipping about 4 months ago. Could this be a worn clutch again, a master cylinder problem or does my pedal just need adjusting, or some other problem. I just replaced the clutch about 4 months ago and I know I haven't worn it down that quickly since I don't race it. I just drive it normally.