I'm stumped on this noise

[68C15]

My nephew has an 04 K1500 5.3 "T". The other day he said it was making a lifter noise and brought it by my shop for advice yesterday. I couldn't narrow it down with the limited time I had to spare so I told him to bring it to my house today. The sound is strongest on left bank towards rear. This afternoon he stopped by and the noise is louder than last night. We pulled the bank 1 cover and saw nothing obvious.

I'm familiar with the lifter, wrist pin and piston skirt noises these are known for but this dry scrape noise has me stumped. I tried posting a video but something about security token prevents it. The sound is rhythmic and sounds like it's isolated to one cylinder. Disconnecting coils one at a time made no change

Please help, thank you