noise in my 996
 

i HAVE A SQUEAKING NOISE IN MY 2000 996 CABRIOLET. THE NOISE APPEARS AFTER THE ENGINE WARMS UP AND COMES ON WHEN I GET OFF THE THROTTLE. NO NOISE IF RPMS ARE CONSTANT OR INCREASING.
THIS DOESN'T SEEM TO AFFECT PERFORMANCE, BUT IS IRRITATING, TO SAY THE LEAST.
I HAVE REPLACED ALL THE BELTS, REPLACED THE WATER PUMP AND REPLACED SEALED BEARINGS IN THE DRIVE TRAIN. THE NOISE IS STILL THERE.
HELP. ANY IDEAS WOULD BE APPRECIATED.