'psssh' sound when i shift gears..

i have a 91 mazda b2200 5spd...and...

i hear a small pssh sound when i let off the clutch, but only going into a gear...

not if im just sitting there in N pushing the clutch in/out.

wuts goin on??? lol, pressure plate/clutch? is one of em goin out? time to drop in an rx7 transmission eh? lol