2007 engine does not run like 2006 engine.

[finall]

Just traded in our 2006 H2 for a used red 2007 H2 SE with 11K miles. Real beauty. But does not sound nice. The 2006 engine was very smooth idling, and had strong pull through all rpms.

But the 2007 engine has a noticeably louder and rougher idle. A bit of a growl. Slight vibration clinking noise from under the hood that was not there on the '06. Sounds a bit like an aftermarket exhaust (but it is stock of course). The growl grows when accelerating from a stop with increased foot pedal travel and rpms, until the vehicle reaches about 30mph. Can't see anything.

The 2006 was noticeably quieter at idle, and smoother at all speeds. No growl.

So the first thing I did was change the new oil that the Hummer dealer 2-litre overfilled during a change to synthetic when I finally got the freshly changed over-tightened and siezed oil filter off. Just after they delivered the 2007 H2 SUV to me. Hopefully this screwup on their part did not damage the engine, as it was only driven this way for 50 miles before I got it home.

I am using the same oil, and the vehicles have about the same miles on them. Threw in 2 bottles of injector cleaner into the tank. No difference.

Has anyone else noticed this difference between the 2006 and 2007 models? Is this growl normal, or does the 2007 have something wrong with it? Seems to run fine otherwise. Just more noisy.

Did anything change from 06 to 07 in the engine, tranny, or exhaust that could be causing this difference?

Help!! Anyone who owns or have owned both an 06 and 07?

Help!! The truck has an appointment with the dealer on Monday for this growl, but I would like to avoid taking it in for exploratory surgery if it is not needed.