I read through much of this thread but not all. Thanks to Al for the straight scoop, which was I thought all along. Good luck getting rid of the bog with a tune. Most of us running M6 SSes at the track feel a bog too but it is not as pronounced.
On the stock M6 SS I was able to get a few low 1.9s and with tires low 1.8s. So the best you can do is a 2.0 in an M6 ZL1? I was thinking of throwing a Paxton on my SS or upgrading ($gulp$) to the ZL1. A 2.0 would be disappointing to me. Still on the fence though.
My CA6 ZL1 bog theory was the weakness of the diff. It is really built for the road track and not so much for the 1/4. Also I think the strength of the diff on the SS and ZL1 are about the same. This would benefit the SS and save Chevy a few $$. Am I wrong here? I do know the CA6 SS diff is much stouter than the 5th gen SS diff and that was on a heavier car. I have ridden home in a flatbed with my 5th gen 1LE. I think I am safe in the CA6 SS so far. The Ca6 SS axles can snap, but they are like a shear pin on an outboard motor and cheap to replace. Good call Chevy engineering.
In the 5th gen ZL1 you had the Grave Digger diff with no worries about breakage. But man that sucker was heavy. I had to lift one in and out of my Rav4. My back still hurts. So with the lighter (and very impressive) CA6 ZL1 you get the lighter car and a little built in protection. I think a good trade off. Very few ZL1s ever see a drag strip. I rarely see one at Atco. But will I buy one? Given my car love for the 5th gen ZL1 I know I would like one. Can we get a group buy together?
All this being said I am very jealous of watching M6 S197 bolton GTs dipping deep into the 11s with 5K clutch dumps, getting a little air under the front tires, and very low 1.5 60's. But then I do love the IRS on a mountain road. We must Compromise to have one car to do it all. The Camaro comes very close. Hats off to GM engineering building this car for us motor heads. But if there is a next gen Camaro can you make it a little easier to see out of? The Mustang has a better compromise here.