I have an 06 LQ4 all stock with about 165,000 miles on it. Runs very well . Always maintained at the recommended intervals. Oil was just changed several weeks ago. I started noticing mechanical tapping noise somewhere in the range of 2500 rpm to 3500 rpm. It is not dependent on engine load. Has anyone ever seen these lifters lose pre-load and start making noise? Any other ideas? This is my daily driver and I don't have time to tear it apart, but not excited about potentially being stranded either. Think I am going to pop the valve covers off this week and see if there is anything obvious. Let me know your thoughts and if you have any recommended things to check. Thanks.

 

Lifter is possible, I would check for loose spark plug, or broken exhaust manifold bolts.

 

If it IS lifters, it's just time catching up with it all. Go a notch up on oil viscosity and see if it lessens or disappears.