I have been dealing with this problem for a year now on my 98 LS1, and nothing I do seems to fix it. Also keep in mind that I have swapped heads, intake, and throttle bodies all while this problem remains constant.
When I rev the engine, or come back down to idle when coming to a stop light etc. the engine almost dies. Usually it catches itself, but sometimes it dies. If the engine does catch itself, it will then stable itself out. If I let it idle without reving it up, it will idle all day without a problem. It's just returning to idle where I have the problem. It also seems like the problem gets worse the higher I rev the engine.
Looking at the log, there aren't any obvious signs as to what is causing the problem. The IAC position is returning to the normal spot, and the spark advance seems to be ok.
*new issue* A new issue that has appeared in the last week is that when I start the car up, the IAC position hangs at 0 for a couple minutes until it shoots up to about 140. I have to keep the car running with the throttle or it will die. I've also noticed that the IAC position is barely moving when I rev the car up.
Take a look at the log and tune. The AFR isn't perfect and the MAF is switched off because I just made some engine changes, but I was having the same problems when I had the VE tables dialed in and the MAF turned on. I just haven't had time to get the wideband out and tune it again since the changes.
MODS: Stock LS1 bottom end. LG G5X3 Cam. PRC Stage 2.5 5.3L Heads. FAST 90 Intake/90mm TB. Kooks Headers.