how big can they be before you need to port your intake manifold?
if i remember correctly, you cant go too big w/o matching the intake manifold, right?

 

I agreed with JimmyB. TB does work but you gotta becareful, if the TB size is too big and while you are not running cams, it will actually make the car perform worse and pedal feel's sticky which I hated the most.

Sending the stock TB out and get re-worked wil be your best bet.

 

From what I have been told you can go up to 70mm before you need to have the intake manafold ported.