I got a new clutch and also a salvaged clutch master cylinder recently. I have noticed that the engage point on my clutch is very close to the floor if the car has been idleing (low pressure?) and after it has been driven, it is at the normal point near the top. Also, if i rev up my engine during idle, the engage point changes from low to normal. What do i need to replace? Slave cylinder?

 

new clutch. happened to me too, just replaced the clutch and the problem is gone now, if you cant afford that you can try adjusting the pedal free-play and getting the lines bled.