Hello, I can't promise that this is your noise, but it must be pretty common if GM went to the trouble of issuing a service bulletin on it. Thanks
Some customers may comment on a vibration/rattle/buzz type noise coming from the right side dash/windshield area. The noise will start when the vehicle speeds reach 56 to 64 km/h (35 to 40 mph) and continue up through highway speeds.
The noise may be coming from the plastic cowl cover screen vibrating and contacting the windshield on the right side of the windshield between the wiper post and the right side "A" pillar. The cover may be raised off the windshield slightly and the air flow as the vehicle is traveling is pushing the cover down, causing the rattle/buzz noise.
Remove the cowl cover and install a strip of double stick tape to the underside of the cover. Install the tape about 102 mm (4 in) from the wiper post opening to the end of the cover. The tape should be on the plastic cover, not on the seal. Clean the windshield in this area and reinstall the cover. Press the cover down where the tape was installed.
3MTM Scotch Mount*
Here is yet another.
This bulletin is being revised to update the parts information. Please discard Corporate Bulletin Number 06-06-02-002B (Section 06 -- Engine/Propulsion).
Some customers may comment on a ticking or clicking noise heard inside the vehicle on the passenger side. The noise may be noticeable with the engine on and at idle, with the vehicle in PARK, and with the HVAC and radio off.
The noise may be caused by normal EVAP purge valve operation. The EVAP purge valve operation may be internally grounding out, creating a noise path through the coolant inlet and outlet hoses/pipes
Perform the diagnosis FIRST to determine if the EVAP purge valve operation is normal. Confirm the customer concern by using a Tech 2® to disable the EVAP purge valve. If the ticking or clicking noise heard inside the passenger side of the vehicle is gone, perform the following steps:
Important: All 2006 models listed in this bulletin use two 10 mm (0.4 in) longer throttle body studs, P/N 11562429.
Tighten Tighten the two studs to 6 N·m 53 lb in)
Tighten Tighten the nuts to 10 N·m (89 lb in).