Rod knock?

[Bobbed72]

Afternoon/Evening all, Got what I am fairly certain is rod knock on a rebuilt 5.3. Started after taking the truck to the drag strip. Ran fine for the year prior.

Problem starts after about 5-10 minutes of driving. Goes away when I let off the gas. I notice the motor is fully warmed up long before the noise starts and the oil pressure remains between 30-40.

Researched the great web in hopes of finding something other than actual rod knock being the problem. Pulled the pan and checked the pickup tube oring (should of looked at the rods while I was at it). Didn't see any glitter in the oil pan.

Checked the flexplate cause I heard that they could crack. Solid.

Checked the rockers for anything loose. All good.

Considered detonation. My AFR's look good overall but I'm only monitoring the left side of the motor. Reduced my timing (engine is carbed) across the board by a few degrees and the noise is all but eliminated. Is there anything that could of made detonation suddenly a problem? or are the lower cylinder pressures reducing the knocking force?