A larger throttle body seems to be one of those "required" bolt ons, but I question whether my particular setup actually needs one. I've been thinking that if a TB is "restricting" the motor, then it should pull vacuum at WOT at higher RPM. My cammed LS setup does not pull vacuum out to the 7600 RPM limiter...my question is basically, am I right in thinking that this means that my TB isn't restricting me? Or can a small TB restrict a motor without showing vacuum?
:edit:
The same question applies to my intake pipe...right now I have an LS sized intake arm...I know the 3" intake arm is recommended for most setups, but is it restricting me in some way I'm not seeing/thinking of?

 

well, an anti-reversion step with your TB is the first way to set up creating positive pressure in your manifold. If the motor is a pretty healthy motor which it seems to be than you might wanna up it a little bit. If you open the intake manifold opening to 4mm larger than your tb opening this will create the anti-reversion step. same with the head. only port matching the intake ports and not the manifold ports. I know someone who has and is currently building some incredible D motors, like at 150hp per liter uses a stock 55mm d series TB and 2.5in intake, granted that motor is a little smaller but so is his TB compared to yours.