You could do every single modification possible for the pre-2011 V6's and it will only give you maybe +15hp. You're really throwing your money away when trying to mod the V6's. I've been there and done it.
A throttle body will not only NOT make your car any faster, it will make it slower. A CAI will add maybe 1-2 HP, if that. The muffler will do absolutely nothing, same with a tuner. The only way to make a pre-'11 any faster is with forced induction (supercharger or turbo).
I once was in the same boat you're in. I had a V6 and had money to spend to make it faster. After a lot of research and trial-and-error, I realized that modding the V6's is just a waste of money. I learned the hard way and threw money down the drain.