Hello all. The engine in question is an 8.1l vortec with minor internal modifications, slight over-bore, mildly ported heads, and small cam upgrade, 4l80E trans (also pcm controlled).
I'm trying to gather as much info as possible while trying to figure out which spark correction PID's are actually applicable and correct for this application without logging 30+ channels so please bear with me
First to just address it ahead of time; yes, the log does show that I am seeing some Knock Retard at various conditions, but am currently working that out separately and it does not seem to the culprit of the issue I am looking into here.
Timing when rolling into the throttle hard from idle is dipping well into the negative values (sometimes 30deg less than the main spark table!). When I account for all of the corrections that seem to correlate as they should, they still just don't add up to that timing difference and it seems there is a hidden force at work here...

"Trans Torque Reduction Spark Retard" (GM.EST XMSN DMA) seems to be very active in showing spark retard, but does not seem to correlate to actual timing advance (timing comes back up after the dip even though trans spark retard stays high). The tune file also has all of the torque control (aside from shifts) set to disable and table values zeroed out.

A log file example of the issue and the current tune file are attached. Frame numbers of most interest in the log file are: 826, 1131, 1816, 1922, and 2558 (in that last one, I loaded the engine up some first before throttling all the way up to WOT)

Next logs, I plan to add "EST Base Spark" and "EST Run Spark" to try to gain some more insight.

Anyone have any idea of what may be killing my timing here, or any parameters or tables I may be missing or need a closer look at?

Thanks!

Spark Retard Example 1.efi
040716 modT - DFCO.ctz