My L99 seems to run fine.
I had a long on-ramp getting on the freeway, so I tested it. Spun up to 5800-6000 before shifting to second with tranction control on. Had to get out of it to merge onto freeway. Seemed ok, but I may not know the difference.
If GM does come up with a fix, you can bet I will do it anyway. Got a need for speed.....safely.