do i really need 3" exhaust

Rod, you'll have more power on the street then you could ever really use regardless of the exhaust size. If you're more comfortable with the 2 1/2 pipes, go for it. It will certainly be quieter then the 3's and you can always open them at the track if you want to get the most out of your combo.

Just for my personal knowledge, i am curious as to your primary header size? I'm not real familiar with all the TTI offerings, but it sounds like the 1 3/4-1 7/8 step would best fill you needs with the 408?