[A4] Strange Sounds

[Zori and Richard Valasek]

HAVE A 98 A4 QUATTRO MANUAL AND AM HEARING A "CLACK-CLACK-CLACKING" NOISE
WHEN THE ENGINE IS COLD AND ACCELERATING THROUGH THE GEARS THE FIRST TIME.
THE SOUND IS MOST PRONOUNCED RIGHT AFTER THE CLUTCH IS LET OUT AND THE SOUND
WILL GO AWAY IF I BACK OFF SLIGHTLY ON THE GAS PEDAL.  THE SOUND IS ALSO
PRESENT EVEN WITH A WARM ENGINE AFTER THE CAR HAS SAT FOR A PERIOD AND AGAIN
DURING THE FIRST FEW ACCELERATIONS.  OTHER THAN THAT, THE CAR RUNS REALLY
WELL.  MILD MODS INCLUDE A FRONT MOUNT INTERCOOLER, K & N FILTER, AND BORLA
EXHAUST--NO CHIP AND NO CHECK ENGINE LIGHT.  COULD IT BE THE ECU OPENING THE
WASTEGATE TO LOWER THE BOOST DURING THESE CONDITIONS?  ANYBODY HAVE ANY
IDEAS?

THANKS FOR ANY HELP.

RICHARD
98 A4 QUATTRO
03 PASSAT V6 4 MOTION WAGON