2000 xlt - I have replaced the cam synch,cam sensor,throw out bearing,slave cyl,and ran the motor WITH and WITHOUT the belt on. We just tore it completely down and replaced all seals and bearings, and pulled the IAC while running and I have an unrelenting noise. Its a constant bwoop,bwoop,bwoop about every 2 seconds. Rpms dont change the speed or sound of it. Drove it home tonite and it runs like a top, plenty of power, same mileage but OMG the sound is embarrassing and loud. 3500 rpms or idle, same sound and same repetition. It will relent for a second or two if I stand on the gas, but then it's right back to bwoop, bwoop, bwoop.

When I plugged in the OBDII scanner it said nothing's wrong, truck's perfect! Run it! If only the scanner had ears. I would really appreciate any suggestions. Thanks!