I replaced my PS reservior and that sound went away. I still have your exact same problem/noise - A constant howling sound while cruising rpms (2800 range) only in 3rd-6th gear and before I am showing boost. Were you able to eliminate the noise?

 

"howling" is often a wheel bearing gone bad. common problem as they age.

does anyone have a lexicon of common porsche turbo noises we might cross reference? "howling, whining, honking and screaming". yeah, that's my girl.

 

I would be surprised if I had a bad wheel bearing. I noticed the sound at 18k miles when I bought the car a couple months ago. I now have 22.5k on the car. I'll take a look at it.

 

i'm not sure about ( low ) mileage being a factor any more when we consider the average age of our cars. the only " howling" i've ever heard from my car was a bad wheel bearing. similar conditions as you've described. that's partly the reason i suggested we could use a lexicon of "sounds to issues" cross ref.

because, one man's "howl" might be another man's "whine". GL w it.

 

PS pump replaced during GT2 clutch slave conversion. ZERO PS noise in my car. It is def. powertrain/gear noise. Ever so slight whine while cruising and 100% not apparent under any type of load (1% to WOT) Only noticeable with windows up and radio off. Transmission and diff fluids changed in spring this year. I hear it is a common noise for the 996tt

 

I just had the p.s res fixed under warranty and that same whistling noise went away. However, now I'm left with a very stiff clutch pedal at start-up. I'm not sure if this is tied to the p.s res fix or if my accumulator is going bad? Now that the whistling is gone I can hear all the rattles in the conv top and dash. Not sure which one is worse!