Having trouble with my 6 speed auto in my 2006 S. Everything I've read points to a valve body, erratic shifting on up-shifts and down. Like it's not sure what gear to choose. Anyone here replaced theirs and have any pointers if so.

Also at 145,00 miles the supercharger seems down on power, no noise. Looking at either a re-built or upgrading to a JCW for about 400.00 more.. Can't find any information on the differences between the stock and JCW supercharger unit. And any changes that would need to be made, and any other parts I'd need to swap.
Thanks