Only used my cc with my mt-82 in 5th and 6th never bothered to check to see if any other gears worked. You really don't need it in 1,2,3,4, but yeah 5 and 6 which happens to be the 2 overdrive gears in a tremec! I've also noticed a trend when following t-56 threads guys that install themselves seem to have this issue more often then guys who have it installed! So that tells me its tune related!
I would much rather install a transmisson myself then pay a shop to do it. Learn more about the car and save money for other mods.
Reminds me of the guy sitting on the side of the freeway and his car is broken or acting funny, I pull over to help him out, guy says IDK I didnt build it, I drive away.