Mitsubishi Repair Problems? Ask a Mechanic for Answers ASAP
Before considering there being an issue with the clutch.... take a look under the driver side dash at the clutch pedal and bracket itself and make sure nothing is unusual there. The reason being we have seen a few instances where people have "upgraded" the clutch at replacement time, and actually created an issue in the process by incorporating higher tension springs on the pressure plate that resulted in deforming of the clutch pedal/bracket, causing rather unusual pedal feel to come and go.
If the pedal looks fine and all, the only things I could really expect here would be either some heavy sediment/rusting inside the system (specifically making the slave cylinder travel more labored) or an actual condition with the clutch itself (spring broken, etc).What I would be doing here first is try flushing the system out with DOT4 fluid, running a pint or so through the clutch hydraulics and see if the condition improves. DOT4 is a flushing fluid that will help clear up sediment in the lines/slave including scaling and as hell is arguably more stable at higher temperatures which may help as well.If the flushing of DOT4 improves it some but not enough, get the system hot enough that the pedal is hard to operate again and try cracking open the slave bleeder and see if the difficulty remains. If it does, then there is some seizing in the master (highly unlikely). Otherwise then I would suspect the slave cylinder itself is causing you issues. If the flushing causes zero change to the situation, I would want to pull the transmission and inspect the clutch (disc and pressure plate).