[Seth Stevenson]

Hey, folks. I'm hoping for wiser minds than my own to chip in with a noise that has me flummoxed. I'm a bit of a novice when it comes to working on and diagnosing cars, although 2 years of owning and working on a Porsche has been quite a satisfying education.

I drive an 86 951/944 turbo with a manual limited slip differential. About 3 months ago, I started getting a weird rubbing/whining noise at higher RPMs. The noise is:
1. Not detectable in 1st or 2nd gear. It tends to appear only rarely in 3rd gear, and regularly in 4th and 5th gears.
2. Present typically between 2000 and 3200 rpm.
3. More prevalent at higher temps.
4. Seems louder inside the cabin than outside, and seems to be coming from either the "rear" of the engine bay, where it meets the cabin, or alternatively the front right of the car, near the power steering pump. (I'm half deaf, so these are tentative diagnoses based on friends and family.)
5. Independent of turning.
6. Tends to be worst when the engine is under load, when the accelerator is depressed.
7. It is usually "cured" or terminated by depressing the clutch. However, if the car is in neutral and the engine is revved, then the noise is sometimes reproducible.
8. It seems to be getting worse.

I have recently replaced all wheel bearings, belts, and vacuum hoses. I have replaced the transmission/differential oil. None of these has helped.

The fact that it is not changed by steering direction seems to rule out bearing and steering pump issues, and the continued presence of the noise when the clutch pedal is depressed or the transmission is in neutral seem to rule out the clutch or transmission.

I'm wondering if it could be the flywheel itself or the pressure plate, but I'm out of my depth in terms of definitively diagnosing the problem.

Any suggestions are greatly appreciated. Thanks!