2009 LGT 5MT feedback knock of -11 on stage 1

I ran the Cobb stage 1 93 oct tune on my 2009 LGT 5MT (59k original miles) for a while, but reverted to stage 0 b/c I was seeing feedback knock of -11 sometimes. It only ever lasted a few seconds (like maybe 5) when it did happen.

Sometimes it was under load and other times I'd see -6 to -11 at 65 mph, in 5th gear, on a straight or very small incline on the highway with cruise control on.

I always run 93 octane. The vast majority of the time it's from QuikTrip in the DFW area. I try to stick with Top Tier providers.

From all I've read, I wonder if it's heat soak on the OEM TMIC. Do you guys concur? Or does it sound like something else? And how do I go about eliminating possible causes? For one thing, I know the stock heat shield is not loose, so I don't think it's false knock from that.