OK. So electronic TB.
Oh, I'm newbie enough I had to Google tip in.
Me? I'm considering connecting with another 986 owner, local, and get their opinion on the sound.
Next, I'm tightening all screw/bolt connections relevant to the TB.
I'm next disconnectng the electrical harness from the TB and spraying/cleaning it with electrical cleaner.
Do you hear the sound from the cockpit... or do you have a helper give it gas/pressing the pedal... with you at the sound source? With your ear ON it, that might reveal a culprit.
I'm next, and carefully due to brittle hoses, disconnecting/connecting hoses listening for irregular sounds or changes in engine RPM.
Are the intake boots, connecting the manifolds, properly installed and tightened?
If you're hearing the hiss momentarily, methinks that once there's sufficient pressure, the leak is reduced by the laarger amount of air passing through. I know... not a scientific description... but a more technical member might chime in correcting me where I'm wrong.
Good luck! Report back.
