If you unplug the IAC and it acts normal, then your problem is not the clutch master cylinder which has no relationship to idle.
Do you still have the old IAC? If so, I'd recommend cleaning it, and re-installing it. It was probably merely dirty. Also clean the throttle body and throttle plate. The best thing to use is simply a rag and elbow grease. You can put a dab of carb cleaner on the rag, but I would not spray it inside the TB. I worry about chemical reactions between the chemicals in the cleaner and the TB. No issues have been reported, but since it can be wiped out with a simple cloth, I typically choose the simplest method.
Clean the IAC with carb cleaner, and be sure to use a Q-tip to move the plunger and clean the outside of the plunger. Allow to dry.
You might also want to clean your MAF while you're at it using spray MAF cleaner.
Once you've done all of this, remove the negative battery terminal for 5 mins or so, and then put it back on. This will reset your fuel settings. Start the engine, and do not touch the accel. Allow it to idle for 5 mins after the idle settles down to about 1k rpm. If the idle never settles down, then you have a mechanical problem somewhere. During the 5 min period, you will notice slight fluctuations in the idle, that is normal. The ECU is testing for the optimal settings, when it is finished, the idle will drop down to 7-800 which is where it should be normally. If you touch the accelerator during the test, the test will reset and start over again.
You might be able to get away with trying just the A/F reset procedure as described above- assuming that the IAC you just replaced is good. I always try cleaning the original IAC first. More than half the time that solves the problems. If the seal around the outside of the plunger is damaged, then the IAC is no good, so don't bother cleaning it. If cleaning doesn't make it seat completely sealing off the two chambers from each other, then it's probably not good either.
