Googling around about TCC slip I found a discussion on a grand prix forum about this here https://www.grandprixforums.com/1997...-slip-rpm.html. Interestingly they also mentioned KR in what sounds like the same area I am seeing it. I wish they went into more detail though

Edit: Okay so I found a few more threads about this, I guess maybe its a common issue? https://forum.hptuners.com/showthrea...ith-TCC-locked. This guy has what appears to be the same issue as me except for the fuel trims leaning really really far out. Apparently his issue was a exhaust leak between the head and rear exhaust manifold? I do have headers and this low RPM load knock has been an issue since roughly the header install, based on my scan gauge. Of course I don't have tune data from that far back, and I could have just been noticing the KR on the gauge because I started learning and paying more attention to the car, but who knows. I guess I'll see about checking the header gaskets.

I don't think an exhaust leak would cause the knock sensors to trip. You also said you put high octane in and the knock went away for the most part. That would pretty much rule out an exhaust leak as the cause. I'm thinking if the converter is slipping or somethings wrong with the TCC, then it's vibrating the trans and creating knock.

It removed the WOT knock, not the low RPM knock. Also if the TCC was slipping and vibrating the trans the race gas wouldn't remove the knock in that case either.

Yeah, its a tricky problem you've got. I just went out and gathered my own TTC slip data. I tried to replicate the same conditions I saw with that spike of yours. I was in 4th, TCC locked, TCC slip at 20rpm. I stabbed the throttle and the TCC unlocked immediately, no rpm spike.

How many miles does your car have? I might give a local transmission shop a call and ask them about it.

I just hit 240K You could look at a replacement torque converter. Precision of New Hampton is a good converter company and they have stock converters at autozone for 160$