07 5.3 Nbs High Rpm Rattle?

[vortec327]

07 GMC new body RCSB 5.3

 

6500 miles

 

The other day hitting passing gear getting on the freeway i notice a loud rattle comming from the engine area just before the shift point. Sounds just like pinging/detonation. So i try a tank full of some highrer octiane fuel (91) from a different station and i still here the noise. I even tried a fuel additive with no luck. Also does the active fuel management have anything to do with engine noise? The rattle only happens at 4500 RPM to shift point, in passing gear. ie 30mph punch and 70mph punch. Definetly going to make an apointment with the dealer next week to see whats up. Any ideas? All i have done to the truck is added a K&N FIPK.

[nbscanuck]

It actually might be a loose heat shield on the exhaust. Crawl under and poke around.

[vortec327]

It actually might be a loose heat shield on the exhaust. Crawl under and poke around.

 

Checked for loose heat shields and everyting is tight. Going to take it to the dealer, sound is getting worse. Will update on the problem when fixed.