Mine is still hissing. I've replaced the check valve and it didn't fix the noise. The tank seems to be fine, no cracks. Not sure what else to try.
i had the same problem, dealer replaced the HVAC controller (not official name, i will have to look at the paperwork to get the name) but i believe it was a "vacuum manifold" no more noise.
I checked all my connections and they are solid. Not sure what to do now other than taking it to the dealer and paying out the rear for something that's probably an easy fix but I'm just not seeing it. Autobahn, check http://www.fordparts.com Part # YG-360 A/C Control Module; Check Valve
I picked up the part posted here and installed it (super easy) and it fixed the hissing. I can now hear my magnaflow!
Thanks for all the help guys
Has anyone actually found a 100% fix for the turbo whistling sound on acceleration?
I had been hearing a hissing noise any time I accelerated. I discovered the sound was coming from the vacuum reservoir tank located under the glove box. Is anyone familiar with this issue? Will replacing the reservoir fix the issue? I made sure the T connector with the hose was secured properly. I'm not even sure what the vacuum reservoir tank does if anyone can clarify.