....a TB spacer on the '07-up / TBSS intake manifold? Those IMs are both the same, right?
I'd expect the resultant increased plenum volume to be of more help with larger displacements.

 

I'm sure that nobody here has dyno tested a tb spacer, as it's pretty much common knowledge that they don't do anything on this style intake with fuel injectors at each port. The carbureter style throttle bodies are different, and respond to the tb spacers as the fuel and air are mixed and atomized in the intake, as opposed to the combustion chambers on the multi-port intakes. Do yourself a favor and don't waste any money on a tb spacer=gimmick.

 

They make a great paperweight