im not a tech or ne thing but i can relate. my car did that to me in the same gear at the same rpm. as far as the clutch pedal gettin soft i dunno.
but ne ways the car did it to me on about 3 diff. occasions my uncle is a mechanic and so i took it to him. he came to the conclusion that the car was running to lean, because i was pushing to much boost with stock injectors. i put bigger injectors in and it hasnt had the problem since.

if you want better advice pm dsminduction he knows alot and has helped
me with alot of stuff... good luck