this depends on the application and what else is currently on the car.... what are your plans for the car?
JG Intake Manifold:
high RPM N/A (above 9K)
High boost
Skunk2:
below 9K RPM N/A
low to moderate Boost
On most N/A applications I have seen around town, a bored out TB to 64mm would be plenty...
My opinions are worth as much as you paid for them.