OK, having a very unusual sound in a MK4 Golf TDi ALH. It only happens under moderate (normal) acceleration and only in 1st or second gear. It starts at 2800 and continues to 3800 RPM. It sounds somewhat like a brake squeal in nature, but more like when you make a crystal wine glass 'ring' by rubbing the rim much like a pulley ringing. I've checked things out with VagCom and found nothing. I've lifted the car up and put it in gear accelerating through the RPM range and nothing. Pulled the wheels and checked all associated moving parts for unusual wear. It never happens in any other gears or at any other RPM ranges. Brakes are good, no obvious play in the front wheel bearings. Axles/boots are all good. I visually inspected all drivetrain parts and see no rubbing or indication of chafing anywhere. No apparent soot from EGR pipes. Some oil in the boost pipes, but just a coating. The sound comes from the front of the car and seems like it's from the driver side. Recent changes to the car in the last 10k miles are a new 100k timing belt, all timing pulleys, water pump, serpentine belt, and the car was chipped w/ new nozzles. Timing belt and path looks clean and VCDS tdi fuel timing checker is just a little advanced. Checked the EGR system and there are no sooty leaks indicating a problem there. Troubleshooting today, I found the VNT actuator sticking. Removed, cleaned, verified, and replaced. Pulled the serp belt and verified correct function of the clutched alternator pulley. Operates properly, but replaced anyway because I don't know how old it is. New one was stiffer in freewheel direction. Did vacuum testing and found that the small line from the vac pump at the valve/tee does not hold vacuum (removed small line from the tee, applied mityvac to line). Troubleshooting indicates that the N75 valve allows air to pass when mityvac is on the top nipple, car turned off. Everything else on the circuit holds vac. This doesn't seem right. Should it do that? I'm stumped on the noise. Took a 12' piece of silicone tubing and stuck it in the engine bay near numerous items with the other end stuck in my ear while driving to find the ring. No luck so far. Tried transmission, vac pump, Brake booster, N75 valve, and power steering pulley. Nothing. I'll continue when the wife is done using the car later today. Anyone with ideas?