My clutch pedal feels great when tooling around but if I get on it a bit and either accelerate from a stop aggressively or down shift to accelerate aggressively the pedal becomes very soft and mushy.  After only a minute the pedal returns to normal, feeling nice and tight.  I had the pedal assembly replaced 4 months ago and am experiencing no slippage when driving normally.  Everything feels "normal" otherwise.   Only after a hard acceleration does this happen.  Thoughts? 
