trans troubles

trans troubles

I own a 2002 silverado 2500, with a manual 6 speed, lately the clutch pedal has been stiffening and staying on the floor when i press it, but is fine when i pull it back up with my foot. The truck is chipped and the clutch pedal only does this at high levels of torgue and excelleration. I cant narrow down what it is. If anyone has a clue, beside the chip and my heavy foot, i would appreciate some advice.